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Networking Tutorials

Computer Peripheral Devices and Their Functions Explained

This tutorial explains computer peripheral devices and their function in details with examples. Learn how computer peripheral devices (such as RAM, ROM, processor, input and out device, motherboard and storage device) work with functions and specifications.

Bits & Bytes

Computers are devices powered by electricity, which has two discrete states: On or Off.

  • To be processed, all data in a computer system (words, symbols, pictures, videos, sounds) must be reduced to a string of binary digits.
  • A binary digit 1 or 0 is called a bit,
  • Eight bits grouped together as a unit are called a byte, which provides enough combinations of 0s and 1s to represent 256 individual characters, including numbers, upper and lower case alphabet letters, punctuation marks and other characters
Name Abb Approx. Bytes Exact Bytes Approx. Pages of Text
Byte B One 1 One character
Kilobyte KB (or K) One thousand 1,024 One-half page
Megabyte MB One million 1,048,576 500 pages
Gigabyte GB One billion 1,073,741,824 500,000 pages
Terabyte TB One trillion 1,099,511,627,776 500,000,000 pages
Coding Schemes

Define the patterns of bytes

Coding schemes, such as ASCII, EBCDIC, and Unicode, provide the means to interact with a computer

When a letter is pressed on a keyboard, the electronic signals are converted into binary form and stored into memory.

The computer processes the data as bytes of information and converts them to the letters we see on the monitor screen or on a printed page.

computer coding

The System Unit



The System Unit houses the central processing unit, memory modules, expansion slots, and electronic circuitry as well as expansion cards that are all attached to the motherboard; along with disk drives, a fan or fans to keep it cool, and the power supply.

All other devices (monitor, keyboard, mouse, etc., are linked either directly or indirectly into the system unit.

Front of the System Unit

Drives are housed in drive bays which are accessed at the front of the case.

Internal drives, such as the hard disk drive, are installed in internal bays that are not typically as accessible as the external drives pictured here.

front pannel

System Unit cases come in a huge array of types and styles, depending upon hardware needs.

Types of Ports

serial port

Serial ports



transmit data one bit at a time, like the picture on the left illustrates.

Parallel ports

transmit more than one byte at a time.

These types of port designs are based on whether or not fast data transmission rates are required by the device or not.

Most computers come with basic types of ports (serial, parallel, keyboard, mouse, and USB); and expansion cards allow you to expand the available types needed by specific devices.

Different Types of Connectors

connector

Understanding the differences among connector types is useful and important, as the cable required to attach a device to your computer is specific to its connector, not to mention the port on the computer.

Non-Volatile Storage Devices

Disk drives

  • Internal & External
  • Hard drives
  • Removable disk drives
  • Floppy disks (1.4 MB)
  • ZIP disks (100/250 MB)
  • CD-ROM (700MB), DVD-ROM (~5GB/side)
  • read only (-ROM), write once (-R), re-writeable (-RW)
  • Combination drive
  • CD-RW/DVD-ROM, CD-RW/DVD-R

Many other forms
Memory Stick, MultiMediaCard, CompactFlash, and SmartMedia

Hardware components

Input devices –

accept data or commands in a form useable by computers

Output devices

display the processed information – printers, monitors, speakers.

Processing devices

in system unit and are comprised of circuitry.

Storage devices –

Drives read from and write to storage media (the physical material that can store data and programs).

Communication devices

provide connections between computers and communication networks, allowing for exchange of information and data with other computers via transmission media such as cables, telephone lines, and satellites

input_outputSystem

Input Devices
  • Keyboards
  • Pointing Devices mouse, trackballs, joysticks, touchpads and light pens
  • Source Entry devices Scanners, Audio input devices, video input devices, digital cameras
Output Devices
Softcopy

Monitor /Display Screens CRT and Flat Panel (LCD), EL and gas plasma

Monitor /Display Screen clarity

Resolution
refers to the number of dots displayed in the X (across) and Y (down) co-ordinates.
expressed in terms of horizontal pixels X vertical pixels.
Typical screens are capable of displaying 640×480 dots

Dot Pitch
measurement of how close together the pixels, or phosphor dots, are that make up an image.
The smaller the dot pitch, the crisper the image,0.31 or less provides a sharp image, especially when displaying text.

Refresh rate
the vertical frequency, or the rate at which each pixel on a screen is re-drawn. A low refresh rate results in an image that flickers, resulting in eye-strain.
A refresh rate of 60Hz means the images is redrawn 60 times a second. Typical refresh rates are 60Hz, 72Hz and 75Hz.

Video Display Adapters

Display graphics – Visual output from your system.
Works between the system\’s processor and monitor
Relays the information received from the programs and applications running on the system to the monitor

VDAs come with their own memory chips (RAM or VRAM for video RAM) which determines how fast the card processes images, the resolution, and how many colours it can display.
VDA embody certain standards.
Todays PCs commonly use VGA and SVGA standards

Hardcopy Output : Printers
Impact Printers

The general features of impact printers are uses force by applying hammer pins to strike the paper

  • slow speed
  • prints on most paper types
  • transparencies not supported
  • multiple copies may be printed at once

Advantages : Less expensive, Fast (some types) , Can make multiple copies with multipart paper

Disadvantages : Noisy! Print quality lower in some types. Poor graphics or none at all.

Dot-Matrix and Daisy-Wheel.

Dot matrix printers form characters using row(s) of pins, 9, 18, or 24 which impact the ribbon on top of the paper.

Daisy wheel printers use a spoked wheel with characters placed at the end of each spoke. A print hammer is used to strike the desired character onto the ink ribbon and then the paper.

Hardcopy Output : Printers
Non Impact Printers

General features print head does not make contact with the paper

  • higher speed in characters per second is possible
  • prints on most paper types but better quality obtained with better paper
  • transparencies usually supported
  • Uses ink spray or toner powder
  • Offer superior quality and greater options (in terms of the number of fonts and quality of graphic pictures)

Disadvantages : more expensive.

The three main types of non-impact printers are laserjet, inkjet and thermal

Characters of printers

Speed: The speed of a printer is measured in: cps= characters per second, lpm= lines per minute ppm= pages per minute The faster the printing, the more expensive the printer.

Resolution: A more numerical measure of print quality is printer resolution. Measured in dots per inch (dpi), this determines how smooth a diagonal line the printer can produce.

Cable connection:

Serial Cables- send data only 1 bit at a time- Distance from PC 1000 ft

Parallel Cables- send data 8 bits at a time. Distance from PC 50 ft.- Most popular – USB cable which has a maximum data transfer speed of 12 megabits/s (1.5 MBYTES/s).

The Motherboard

The motherboard is the main circuit board of a computer. It contains the central processing unit (CPU), the Basic Input/Output System (BIOS), memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers for standard peripheral devices like the keyboard, disk drive and display screen.

The chipset and other motherboard circuitry are the \”smarts\” of the motherboard. Their job is to direct traffic and control the flow of information inside the computer.

The chipset is a critical part of any computer, because it plays a big role in determining what sorts of features the computer can support.

motherbord

BIOS
  • BIOS stands for Basic Input/Output System.
  • lowest-level software in the computer
  • Acts as an interface between the hardware (especially the chipset and processor) and the operating system.
  • The BIOS provides access to the system hardware and enables the creation of the higher-level operating systems that you use to run your applications.
  • The BIOS is also responsible for allowing you to control your computer\’s hardware settings, for booting up the machine when you turn on the power or hit the reset button, and various other system functions.
ROM: Read Only Memory
  • ROM is nonvolatile. ROM chips contain permanently written data, called firmware (your BIOS lives here).
  • ROM contains the programs that direct the computer to load the operating system and related files when the computer is powered on.
  • ROM chips are usually recorded when they are manufactured.

PROM -Programmable Read Only memory chip cannot be changed to update or revise the program inside

EPROM Erasable Programmable Read Only memory Data can be erased and chip can be reused Can be erased by shining high intensity UV light through the window

EEPROM Electrical Erasable Programmable Read Only memory under high voltage

FROM -Flash ROM is reprogrammable memory using normal voltage inside the PC- You can upgrade the logic capabilities by simply downloading new software. This saves the expense of replacing circuit boards and chips.

Processing Devices

Processing Devices

Cache

Pronounced cash.

It is a small, high-speed memory area that is placed between the processor and the system memory.

The value of the cache is that it is much faster than normal system memory.

The most frequently used instructions are kept in cache memory so that the CPU can look in there first – allows the CPU to run faster because it doesn\’t have to take time to swap instructions in and out of main memory.

Large, complex programs such as complex spreadsheets or database management programs benefit the most from having a cache memory available. Pentium II processors generally come with at least 512 KB of cache memory.

Random Access Memory (RAM)
  • RAM is Primary Storage, also called internal storage.
  • Serves as computers workspace, storing all or part of the program that is being executed, as well as data being used by the program.
  • RAM provides instructions and data to the CPU.
  • These instructions/data are coded in bytes.
  • Each byte is placed in a precise location in memory, called an address.
  • To access data or instructions in memory, the computer references the addresses containing the bytes.
  • The amount of memory available is therefore measured in bytes

RAM

  • RAM chips consist of millions of switches that are sensitive to changes in electric current.
  • RAM chips are typically packaged on small circuit boards called memory modules, which are inserted into special slots on the motherboard.
  • RAM is Volatile storage: Power goes, data goes!
  • Data/instructions are copied into memory as needed.
  • Not enough memory or corruption of data/instructions in memory can cause crash.
  • On booting, operating system files are loaded from a storage device (the hard disk, usually) into RAM, and they remain there as long as your computer is running.
  • RAM contents changes as programs are executed.
  • RAM chips consist of millions of switches that are sensitive to changes in electric current.
  • RAM chips are typically packaged on small circuit boards called memory modules, which are inserted into special slots on the motherboard.
  • On booting, operating system files are loaded from a storage device (the hard disk, usually) into RAM, and they remain there as long as your computer is running.
  • RAM contents changes as programs are executed.
  • The amount of RAM needed depends on the types of applications you intend to run on the computer. S/w indicate the minimum amount of RAM required to run.

Two basic types of RAM are Dynamic RAM (DRAM), and Static RAM (SRAM).

Most computers today use DRAM, which are also of two types:

  • SDRAM Synchronous Dynamic RAM runs at the same pace as the system clock runs
  • DDR SDRAM DDR stands for Double Data Rate – runs at double the pace the system clock runs – available in speeds from 266 MHZ upto 600MHZ
  • DDR2 SDRAM runs at four times the pace the system clock runs – available in speeds from 400 MHZ upto 800MHZ

Most desktops and notebooks use one of the three most popular types of synchronous dynamic random access memory (SDRAM) for the main system memory. Single data rate (SDR) SDRAM is the older type of memory, commonly used in computers prior to 2002. Double data rate (DDR) SDRAM hit the mainstream computer market around 2002, and DDR2-based systems hit the market in mid-2004.

DDR SDRAM is a straightforward evolution from SDR SDRAM. The big difference between DDR SDRAM and SDR SDRAM is that DDR reads data on both the rising and falling edges of the clock signal, so the DDR module can transfer data twice as fast as SDR SDRAM.

While DDR has a limited clock rate, the evolutionary changes to DDR architecture enable DDR2 to achieve speeds beyond of DDR, delivering bandwidth of 5.3 GB per second and beyond! Because DDR2 is able to operate with faster bus speeds, your memory doesn\’t hold back the performance of your processor.

Generally speaking, motherboards are built to support only one type of memory. You cannot mix and match SDRAM, DDR, or DDR2 memory on the same motherboard in any system. They will not function and will not even fit in the same.

Why is RAM so important?

Aside from the processor, the two most important factors affecting a PC\’s performance are RAM and hard disk capacity.

Hard disks are typically huge, so the primary limiting factor is the amount of installed RAM.

Without enough RAM, the operating system must swap out storage space with the hard disk. The OS creates a Paging File (swap file) to supplement RAM (workspace). This is Virtual Memory.

Virtual memory is inherently slow! RAM speed can typically be 120,000 times FASTER than the hard disk so the less you must rely on virtual memory (swapping files between RAM and hard disk), the faster your system will perform.

Microprocessor
  • Heart and brain of the PC
  • One electrical circuit in control of another
  • Successive generation of processors
  • 80286,80386,80486 -32 bit interface
  • Pentium family P1, P2, P3, P4 64 bit interface
  • Dual-core technology is like having two processors – A dual core processor is a CPU with two separate cores residing on the same chip
Terminology
  • Hardware (H/w) All machinery & Equipments Computer & Peripherals
  • Peripherals Any piece of hardware connected to the PC
  • Software (S/w) programs- tells the Computer how to perform a task
    • Systems Software (S/w) For managing internal activities & run applications s/w Interpreter bet S/w & H/w
    • Application Software (S/w) – to perform a specific task Custom or Packaged

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

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Networking Tutorials

IPv6 Address Types & Format Explained with Examples

This tutorial explains IPv6 address terminology such as node, router, host, link and network including types of IPv6 address such as anycast address, multicast address, unicast address, link local address, site local address, loopback address, IPv4 compatible address in detail.

IPv6 Address Terminology

Node

Any device that runs an implementation of IPv6. This includes routers and hosts.

Router

A node that can forward IPv6 packets not explicitly addressed to itself. On an IPv6 network, a router also typically advertises its presence and host configuration information.

Host

A node that cannot forward IPv6 packets not explicitly addressed to itself (a non router). A host is typically the source and a destination of IPv6 traffic, and it silently discards traffic received that is not explicitly addressed to itself.

Upper-layer protocol

A protocol above IPv6 that uses IPv6 as its transport. Examples include Internet layer protocols such as ICMPv6 and Transport layer protocols such as TCP and UDP (but not Application layer protocols such as FTP and DNS, which use TCP and UDP as their transport).

Link

The set of network interfaces that are bounded by routers and that use the same 64-bit IPv6 unicast address prefix. Other terms for “link” are subnet and network segment.

Network

Two or more subnets connected by routers. Another term for network is internetworks.

Neighbors

Nodes connected to the same link. Neighbors in IPv6 have special significance because of IPv6 Neighbor Discovery, which has facilities to resolve neighbor link layer addresses and detect and monitor neighbor reach ability.

Interface

The representation of a physical or logical attachment of a node to a link. An example of a physical interface is a network adapter. An example of a logical interface is a “tunnel” interface that is used to send IPv6 packets across an IPv4 network by encapsulating the IPv6 packet inside an IPv4 header.

Address

An identifier that can be used as the source or destination of IPv6 packets that is assigned at the IPv6 layer to an interface or set of interfaces.

Packet



The protocol data unit (PDU) that exists at the IPv6 layer and is composed of an IPv6 header and payload.

Link

MTU The maximum transmission unit (MTU)—the number of bytes in the largest IPv6 packet—that can be sent on a link. Because the maximum frame size includes the link-layer medium headers and trailers, the link MTU is not the same as the maximum frame size of the link. The link MTU is the same as the maximum payload size of the link-layer technology. For example, for Ethernet using Ethernet II encapsulation, the maximum Ethernet frame payload size is 1500 bytes. Therefore, the link MTU is 1500. For a link with multiple link-layer technologies (for example, a bridged link), the link MTU is the smallest link MTU of all the link-layer technologies present on the link.

Path

MTU The maximum-sized IPv6 packet that can be sent without performing host fragmentation between a source and destination over a path in an IPv6 network. The path MTU is typically the smallest link MTU of all the links in the path.

IPv6 Address Format

Whereas IPv4 addresses use a dotted-decimal format, where each byte ranges from 0 to 255.
IPv6 addresses use eight sets of four hexadecimal addresses (16 bits in each set), separated by a colon (:),
like this: xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx (x would be a hexadecimal value). This notation is commonly called string notation.

Hexadecimal values can be displayed in either lower- or upper-case for the numbers A–F.

A leading zero in a set of numbers can be omitted;
for example, you could either enter 0012 or 12 in one of the eight fields—both are correct.

If you have successive fields of zeroes in an IPv6 address, you can represent them as two colons (::). For example, 0:0:0:0:0:0:0:5 could be represented as ::5; and ABC:567:0:0:8888:9999:1111:0 could be represented as ABC:567::8888:9999:1111:0. However, you can only do this once in the address: ABC::567::891::00 would be invalid since :: appears more than once in the address. The reason for this limitation is that if you had two or more repetitions, you wouldn’t know how many sets of zeroes were being omitted from each part.

An unspecified address is represented as ::, since it contains all zeroes.

Types of IPv6 Addresses



Anycast

An anycast address identifies one or more interfaces. Notice that the term device isn’t used since a device can have more than one interface. Sometimes people use the term node to designate an interface on a device. Basically, an anycast is a hybrid of a unicast and multicast address.

  • With a unicast, one packet is sent to one destination;
  • With a multicast, one packet is sent to all members of the multicast group;
  • With an anycast, a packet is sent to any one member of a group of devices that are configured with the anycast address. By default, packets sent to an anycast address are forwarded to the closet interface (node), which is based on the routing process employed to get the packet to the destination. Given this process, anycast addresses are commonly referred to as one-to-the-nearest address.
Multicast
  • Represent a group of interfaces interested in seeing the same traffic.
  • The first 8 bits are set to FF.
  • The next 4 bits are the lifetime of the address: 0 is permanent and 1 is temporary.
  • The next 4 bits indicate the scope of the multicast address (how far the packet can travel):
    1 is for a node, 2 is for a link, 5 is for the site, 8 is for the organization,
    and E is global (the Internet).

For example, a multicast address that begins with FF02::/16 is a permanent link address, whereas an address of FF15::/16 is a temporary address for a site.

Unicast

Unicast IPv6 Addresses
The following types of addresses are unicast IPv6 addresses:

  • Global unicast addresses
  • Link-local addresses
  • Site-local addresses
  • Unique local addresses
  • Special addresses
  • Transition addresses
Global Unicast Addresses

IPv6 global addresses are equivalent to public IPv4 addresses. They are globally routable and reachable on the IPv6 Internet. Global unicast addresses are designed to be aggregated or summarized for an efficient routing infrastructure. Unlike the current IPv4-based Internet, which is a mixture of both flat and hierarchical routing, the IPv6-based Internet has been designed from its foundation to support efficient, hierarchical addressing and routing. The scope of a global address is the entire IPv6 Internet. RFC 4291 defines global addresses as all addresses that are not the unspecified, loopback, link-local unicast, or multicast addresses. However, Figure shows the structure of global unicast addresses defined in RFC 3587 that are currently being used on the IPv6 Internet.
The structure of global unicast addresses defined in RFC 3587 The fields in the global unicast address are described in the following list:

  • Fixed portion set to 001 the three high-order bits are set to 001.
  • Global Routing Prefix Indicates the global routing prefix for a specific organization’s site. The combination of the three fixed bits and the 45-bit Global Routing Prefix is used to create a 48-bit site prefix, which is assigned to an individual site of an organization. A site is an autonomously operating IP-based network that is connected to the IPv6 Internet. Network architects and administrators within the site determine the addressing plan and routing policy for the organization network. Once assigned, routers on the IPv6 Internet forward IPv6 traffic matching the 48-bit prefix to the routers of the organization’s site.
  • Subnet ID The Subnet ID is used within an organization’s site to identify subnets within its site. The size of this field is 16 bits. The organization’s site can use these 16 bits within its site to create 65,536 subnets or multiple levels of addressing hierarchy and an efficient routing infrastructure. With 16 bits of subnetting flexibility, a global unicast prefix assigned to an organization site is equivalent to a public IPv4 Class A address prefix (assuming that the last octet is used for identifying nodes on subnets). The routing structure of the organization’s network is not visible to the ISP.
  • Interface ID Indicates the interface on a specific subnet within the site. The size of this field is 64 bits. The interface ID in IPv6 is equivalent to the node ID or host ID in IPv4.
Local-Use Unicast Addresses

Local-use unicast addresses do not have a global scope and can be reused. There are two types of local-use unicast addresses:

  1. Link-local addresses are used between on-link neighbors and for Neighbor Discovery processes.
  2. Site-local addresses are used between nodes communicating with other nodes in the same organization.
Link-Local Addresses FE8:: through FEB::

Link-local addresses are a new concept in IPv6. These kinds of addresses have a smaller scope as to how far they can travel: just the local link (the data link layer link). Routers will process packets destined to a link-local address, but they will not forward them to other links. Their most common use is for a device to acquire unicast site-local or global unicast addressing information, discovering the default gateway, and discovering other layer 2 neighbors on the segment. IPv6 link-local addresses, identified by the initial 10 bits being set to 1111 1110 10 and the next 54 bits set to 0, are used by nodes when communicating with neighboring nodes on the same link. For example, on a single-link IPv6 network with no router, link-local addresses are used to communicate between hosts on the link. IPv6 link-local addresses are similar to IPv4 link-local addresses defined in RFC 3927 that use the 169.254.0.0/16 prefix. The use of IPv4 link-local addresses is known as Automatic Private IP Addressing (APIPA) in Windows Vista, Windows Server 2008, Windows Server 2003, and Windows XP. The scope of a link local address is the local link. A link-local address is required for some Neighbor Discovery processes and is always automatically configured, even in the absence of all other unicast addresses. Link-local addresses always begin with FE80. With the 64-bit interface identifier, the prefix for link-local addresses is always FE80::/64.
An IPv6 router never forwards link-local traffic beyond the link.

Site-Local Addresses FEC:: through FFF::

represent a particular site or company. These addresses can be used within a company without having to waste any public IP addresses—not that this is a concern, given the large number of addresses available in IPv6. However, by using private addresses, you can easily control who is allowed to leave your network and get returning traffic back by setting up address translation policies for IPv6. Site-local addresses, identified by setting the first 10 bits to 1111 1110 11, are equivalent to the IPv4 private address space (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16). For example, private intranets that do not have a direct, routed connection to the IPv6 Internet can use site local addresses without conflicting with global addresses. Site-local addresses are not reachable from other sites, and routers must not forward site-local traffic outside the site. Site-local addresses can be used in addition to global addresses. The scope of a site-local address is the site. Unlike link-local addresses, site-local addresses are not automatically configured and must be assigned either through stateless or stateful address autoconfiguration. The first 10 bits are always fixed for site-local addresses, beginning with FEC0::/10. After the 10 fixed bits is a 54-bit Subnet ID field that provides 54 bits with which you can create subnets within your organization. You can have a flat subnet structure, or you can divide the high order bits of the Subnet ID field to create a hierarchical and summarize able routing infrastructure. After the Subnet ID field is a 64-bit Interface ID field that identifies a specific interface on a subnet. Site-local addresses have been formally deprecated in RFC 3879 for future IPv6 implementations. However, existing implementations of IPv6 can continue to use site-local addresses.

Zone IDs for Local-Use Addresses
Unlike global addresses, local-use addresses (link-local and site-local addresses) can be reused. Link-local addresses are reused on each link. Site-local addresses can be reused within each site of an organization. Because of this address reuse capability, link-local and site-local addresses are ambiguous. To specify the link on which the destination is located or the site within which the destination is located, an additional identifier is needed. This additional identifier is a zone identifier (ID), also known as a scope ID, which identifies a connected portion of a network that has a specified scope. The syntax specified in RFC 4007 for identifying the zone associated with a local-use address is Address%zone ID, in which Address is a local-use unicast IPv6 address and zone ID is an integer value representing the zone. The values of the zone ID are defined relative to the sending host. Therefore, different hosts might determine different zone ID values for the same physical zone. For example, Host A might choose 3 to represent the zone of an attached link and Host B might choose 4 to represent the same link.

Unique Local Addresses
Site-local addresses provide a private addressing alternative to global addresses for intranet traffic. However, because the site-local address prefix can be reused to address multiple sites within an organization, a site-local address prefix can be duplicated. The ambiguity of site local addresses in an organization adds complexity and difficulty for applications, routers, and network managers.

To replace site-local addresses with a new type of address that is private to an organization yet unique across all the sites of the organization, RFC 4193 defines unique local IPv6 unicast addresses. The first 7 bits have the fixed binary value of 1111110. All local addresses have the address prefix FC00::/7. The Local (L) flag is set 1 to indicate that the prefix is locally assigned. The L flag value set to 0 is not defined in RFC 3879. Therefore, unique local addresses within an organization with the L flag set to 1 have the address prefix of FD00::/8. The Global ID identifies a specific site within an organization and is set to a randomly derived 40-bit value. By deriving a random value for the Global ID, an organization can have statistically unique 48-bit prefixes assigned to their sites. Additionally, two organizations that use unique local addresses that merge have a low probability of duplicating a 48-bit unique local address prefix, minimizing site renumbering. Unlike the Global Routing Prefix in global addresses, the Global IDs in unique local address prefixes are not designed to be summarized. Unique local addresses have a global scope, but their reach ability is defined by routing topology and filtering policies at Internet boundaries. Organizations will not advertise their unique local address prefixes outside of their organizations or create DNS entries with unique local addresses in the Internet DNS. Organizations can easily create filtering policies at their Internet boundaries to prevent all unique local-addressed traffic from being forwarded. Because they have a global scope, unique local addresses do not need a zone ID. The global address and unique local address share the same structure beyond the first 48 bits of the address. In both addresses, the 16-bit Subnet ID field identifies a subnet within an organization. Because of this, you can create a subnetted routing infrastructure that is used for both local and global addresses. For example, a specific subnet of your organization can be assigned both the global prefix 2001:DB8:4D1C:221A::/64 and the local prefix FD0E:2D:BA9:221A::/64, where the subnet is identified for both types of prefixes by the Subnet ID value of 221A. Although the subnet identifier is the same for both prefixes, routes for both prefixes must still be propagated throughout the routing infrastructure so that addresses based on both prefixes are reachable.

Summary tables of IPv6 Addresses

Address Value Description
Global 2000::/3

These are assigned by the IANA and used on public networks. They are equivalent to IPv4 global (sometimes called public) addresses. ISPs summarize these to provide scalability in the Internet.

Reserved (range)

Reserved addresses are used for specific types of anycast as well as for future use. Currently about 1/256th of the IPv6 address space is reserved.

Private FE80::/10

Like IPv4, IPv6 supports private addressing, which is used by devices that don’t need to access a public network. The first two digits are FE, and the third digit can range from 8 to F.

Loopback ::1

Like the 127.0.0.1 address in IPv4, 0:0:0:0:0:0:0:1, or ::1, is used for local testing functions; unlike IPv4, which dedicates a complete A class block of addresses for local testing, only one is used in IPv6.

Unspecified ::

0.0.0.0 in IPv4 means “unknown” address. In IPv6, this is represented by 0:0:0:0:0:0:0:0, or ::, and is typically used in the source address field of the packet when an interface doesn’t have an address and is trying to acquire one dynamically.

In our next article we will discus about special IPv6 address, IPv4 address and their equivalents IPv6 address. And then we learn how to assign these addresses to host, router and other devices.

The following are the special IPv6 addresses:

Unspecified address

The unspecified address (0:0:0:0:0:0:0:0 or ::) is used only to indicate the absence of an address. It is equivalent to the IPv4 unspecified address of 0.0.0.0. The unspecified address is typically used as a source address when a unique address has not yet been determined. The unspecified address is never assigned to an interface or used as a destination address.

Loopback address

The loopback address (0:0:0:0:0:0:0:1 or ::1) is assigned to a loopback interface, enabling a node to send packets to itself. It is equivalent to the IPv4 loopback address of 127.0.0.1. Packets addressed to the loopback address must never be sent on a link or forwarded by an IPv6 router.

Transition Addresses

To aid in the transition from IPv4 to IPv6 and the coexistence of both types of hosts, the following addresses are defined:

IPv4-compatible address

The IPv4-compatible address, 0:0:0:0:0:0:w.x.y.z or ::w.x.y.z (where w.x.y.z is the dotted decimal representation of a public IPv4 address), is used by IPv6/IPv4 nodes that are communicating with IPv6 over an IPv4 infrastructure that uses public IPv4 addresses, such as the Internet. IPv4-compatible addresses are deprecated in RFC 4291 and are not supported in IPv6 for Windows Vista and Windows Server 2008.

IPv4-mapped address

The IPv4-mapped address, 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF: w.x.y.z, is used to represent an IPv4 address as a 128-bit IPv6 address.

6 to 4 address

An address of the type 2002:WWXX:YYZZ:Subnet ID:Interface ID, where WWXX:YYZZ is the colon hexadecimal representation of w.x.y.z (a public IPv4 address), is assigned a node for the 6to4 IPv6 transition technology.

ISATAP address

An address of the type 64-bit prefix:0:5EFE:w.x.y.z, where w.x.y.z is a private IPv4 address, is assigned to a node for the Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) IPv6 transition technology.

Teredo address

A global address that uses the prefix 2001::/32 and is assigned to a node for the Teredo IPv6 transition technology. Beyond the first 32 bits, Teredo addresses are used to encode the IPv4 address of a Teredo server, flags, and an obscured version of a Teredo client’s external address and UDP port number.

IPv4 Addresses and their corresponding IPv6

IPv4 Address IPv6 Address

Internet address classes

Not applicable in IPv6

Multicast addresses (224.0.0.0/4)

IPv6 multicast addresses (FF00::/8)

Broadcast addresses

Not applicable in IPv6

Unspecified address is 0.0.0.0

Unspecified address is ::

Loopback address is 127.0.0.1

Loopback address is ::1

Public IP addresses

Aggregatable global unicast addresses

Private IP addresses (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16)

Site-local addresses (FEC0::/48)

APIPA addresses (169.254.0.0/16)

Link-local addresses (FE80::/64)

Text representation: Dotted decimal notation

Text representation: Colon hexadecimal format with suppression of leading zeros and zero compression. IPv4-compatible addresses are expressed in dotted decimal notation.

Network bits representation: Subnet mask in dotted decimal notation or prefix length

Network bits representation: Prefix length notation only

Assigning IPv6 address to Devices

IPv6 Addresses for a Host

An IPv4 host with a single network adapter typically has a single IPv4 address assigned to that adapter. An IPv6 host, however, usually has multiple IPv6 addresses assigned to each adapter. The interfaces on a typical IPv6 host are assigned the following unicast addresses:

  • A link-local address for each interface
  • Additional unicast addresses for each interface (which could be one or multiple unique local or global addresses)
  • The loopback address (::1) for the loopback interface Typical IPv6 hosts are always logically multi homed because they always have at least two addresses with which they can receive packets—a link-local address for local link traffic and a routable unique local or global address. Additionally, each interface on an IPv6 host is listening for traffic on the following multicast addresses:
  • The interface-local scope all-nodes multicast address (FF01::1)
  • The link-local scope all-nodes multicast address (FF02::1)
  • The solicited-node address for each unicast address assigned
  • The multicast addresses of joined groups
IPv6 Addresses for a Router

The interfaces on an IPv6 router are assigned the following unicast addresses:

  • A link-local address for each interface
  • Additional unicast addresses for each interface (which could be one or multiple unique local or global addresses)
  • The loopback address (::1) for the loopback interface
  • Additionally, the interfaces of an IPv6 router are assigned the following anycast addresses:
  • A Subnet-Router anycast address for each subnet
  • Additional anycast addresses (optional)
  • Additionally, the interfaces of an IPv6 router are listening for traffic on the following multicast addresses:
  • The interface-local scope all-nodes multicast address (FF01::1)
  • The interface-local scope all-routers multicast address (FF01::2)
  • The link-local scope all-nodes multicast address (FF02::1)
  • The link-local scope all-routers multicast address (FF02::2)
  • The site-local scope all-routers multicast address (FF05::2)
  • The solicited-node address for each unicast address assigned
  • The multicast addresses of joined groups

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

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Categories
Networking Tutorials

Network Operating System Features and Functions

This tutorial explains network operating system features and function in details. Learn what is a network operating system and features offered by popular network operating systems (such as Linux, UNIX, Netware, Apple Mac and Windows Server) with functions.

A network operating system (NOS) provides services to clients over a network.
Both the client/server and peer-to-peer networking models use network operating systems, and as such,
NOSes must be able to handle typical network duties such as the following:

  • Providing access to remote printers, managing which users are using which printers when, managing how print jobs are queued, and recognizing when devices aren\’t available to the network
  • Enabling and managing access to files on remote systems, and determining who can access what—and who can\’t
  • Granting access to remote applications and resources, such as the Internet, and making those resources seem like local resources to the user (the network is ideally transparent to the user)
  • Providing routing services, including support for major networking protocols, so that the operating system knows what data to send where
  • Monitoring the system and security, so as to provide proper security against viruses, hackers, and data corruption.
  • Providing basic network administration utilities (such as SNMP, or Simple Network Management Protocol), enabling an administrator to perform tasks involving managing network resources and users.

UNIX / Linux

UNIX, created originally by Bell Labs (under AT and T), is a powerful server operating system that can be used in peer-to-peer or client/server networks. UNIX was the first operating system written in the C programming language. Due to an antitrust ruling forbidding AT and T from releasing operating systems commercially, AT and T released UNIX upon its completion in 1974 to universities, mostly, enabling people to go in and actually view the source code to the system, which enabled coders to reconstruct the basic functions of the original UNIX operating system. From this practice, called reverse engineering, came Linux, which was first developed in the late 1980s by a young student at the University of Helsinki in Finland named Linus Torvalds.



UNIX (and Linux by extension) systems offer the following features:

  • Fully protected multitasking: This means that UNIX can easily switch between tasks without the operating system crashing, because all UNIX processes are separate from those of the operating system. Even if an application crashes, unless it somehow manages to take down the X Windows system with it (which does happen), the operating system just keeps right on humming.
  • High performance and stability : Many servers running UNIX or Linux have run for years without crashing once. The multitasking capabilities of UNIX, along with the rapid rate at which the operating system matures (especially with Linux, which is free and can be changed by anyone), make UNIX or Linux a powerful solution, especially for server systems.
  • Multiuser capabilities : True multiuser systems enable different users to be logged in to the same system simultaneously. In UNIX and Linux, not only can a user log in to the same system at the same time as other users, that user can log in multiple times on the same system as the same user without the operating system batting an eyelash (such things are often necessary when administrating a network, particularly when managing users).
  • Tons of high-quality software : From Apache Server (a Web server that’s used on a whopping 6 in 10 major Web servers on the Internet) to the long-awaited Mozilla.org Mozilla 1.0 open source Web browser/e-mail software (Mozilla is an open source version of the venerated Netscape Communicator) to the powerful free Gimp graphics manipulation software, Linux is packed with tons of free, high-quality software. The trick is that, with UNIX/Linux, you give up compatibility with commercial software that’s available only for Windows and/or Macintosh, currently.
  • Easy customization : While other operating systems seem to offer less and less choice to the user about which applications to install with the operating system (Windows XP is this way), UNIX and especially Linux are the exact counterpoint to that model. With UNIX or Linux, you can actually customize your operating system kernel, stripping it down to just drivers and networking or installing everything possible.
  • Modular architecture : The modular architecture of UNIX (and especially Linux) is directly responsible for how customizable UNIX is. Modular really means just what it sounds like: The operating system is built with a kernel that attaches modules to itself based on what the user needs.
  • POSIX compliance: With a free operating system like UNIX, the different distributions (or flavors) of UNIX quickly became difficult to manage. Currently, hundreds of different implementations of UNIX are available. To enable programmers to have some idea of how to code their software such that it would run on any version of UNIX, the Institute of Electrical and Electronics Engineers, Inc. (IEEE) defined the Portable Operating System Interface (POSIX).
  • Use of TCP/IP as the standard protocol stack: UNIX overwhelmingly uses TCP/IP as the protocol stack of choice. If you consider that the vast majority of the servers that help make up the Internet are UNIX computers of one form or another, you start to get the idea why TCP/IP is so popular.
  • A shell interface: All versions of UNIX (at least those you care about for the exam) include a shell interface of some sort. If you have ever seen your computer use a completely black screen with white words written on it, that’s a shell interface. You simply type in commands at the prompt and hit Enter to execute those commands. The hard part in using these interfaces is simply the effort it takes to learn all of those rather cryptic commands. Making life even more difficult, UNIX is ultimately customizable and can use different shells. The bash shell (likely the most popular shell in use today) and the tcsh shell, for example, have different commands for the same action.
  • A graphical user interface: Although most versions of UNIX (such as Red Hat Linux) include a graphical user interface (GUI) these days, this has not always been the case. Historically, UNIX has been derided for its cryptic interface, and the advent of the GUI into popular UNIX systems was a direct result of this. Popular UNIX GUIs include KDE and GNOME. KDE is mostly used with Linux, but GNOME has versions for the Sun Solaris operating system, and therefore crosses the border from Linux into UNIX proper.
  • Support for dumb terminals: Traditionally, UNIX was used for dumb terminals, and just about all versions of UNIX still include this capability. The traditional dumb terminal model involves one central UNIX server that is used by remote terminals to execute applications. Basically, a user logs in to a UNIX system via Telnet or some other remote connectivity application and uses UNIX commands to tell the remote system what functions to perform. In this way, users can download and check e-mail via a text-based e-mail client such as Pine. The dumb terminal in this form isn’t used much anymore; Web browsers are definitely more than just dumb terminals— and Web browsers are now the clients most often seen by UNIX servers (at least those that make up the Internet). However, wireless devices such as cell phones and mobile Internet e-mail clients such as AOL’s Mobile Communicator device are good examples of modern dumb terminals. The devices have nearly no storage at all, and don’t carry large e-mail clients on the device; the message is simply transferred as text from one end to the other.

Interoperability
Open source software such as SAMBA is used to provide Windows users with Server Message Block (SMB) file sharing.

Authentication:-Centralized login authentication

File and Print Services
Network File System (NFS) is a distributed file system that allows users to access files and directories located on remote computers and treat those files and directories as if they were local.
LPR/LPD is the primary UNIX printing protocol used to submit jobs to the printer. The LPR component initiates commands such as \”print waiting jobs,\” \”receive job,\” and \”send queue state,\” and the LPD component in the print server responds to them.

Security
With most Unix operating systems, the network services can be individually controlled to increase security.



MAC OS X Server

MAC Server

Client Support
TCP/IP file sharing with Macintosh clients using Network File System (NFS), and File Transfer Apple File Protocol 3.0

Interoperability
Mac OS X Server uses the Open Source SAMBA to provide Windows users with Server Message Block (SMB) file sharing. Network File System (NFS) lets you make folders available to UNIX and Linux users.

File and Print Services
Mac OS X Server provides support for native Macintosh, Windows, UNIX, and Linux file sharing. Protocols supported include:

  • Apple file services (AFP 3.0) from any AppleShare client over TCP/IP
  • Windows (SMB/CIFS) file sharing using Samba
  • Network File System (NFS) for UNIX and Linux file access
  • Internet (FTP)

Built-in print services can spool files to any PostScript-capable printer over TCP/IP, AppleTalk, or USB. Macintosh customers can use the LPR support in Print Center or the Desktop Printer utility to connect to a shared printer. Windows users can use their native SMB/CIFS protocol to connect to a shared printer.

Print services for OS X Server

Macintosh and UNIX (LPR/LPD)

Windows (SMB/CIFS)

Security

  • Multiple-user architecture and user-level access privileges.
  • Secure Sockets Layer (SSL) support provides encrypted and authenticated client/server communications.
  • Secure Shell (SSH) provides encryption and authentication for secure remote administration.
  • Kerberos support for centralized login authentication.

Netware

NetWare has been a great LAN operating system for years, but only recently (with NetWare 5.x has NetWare moved beyond the LAN to where it can easily be a part of larger networks. Until quite recently, Novell NetWare used to be the single most-used network operating system (NOS). However, first Windows NT, and Windows 2000 and Linux, have steadily eaten into the NetWare market share for network operating systems. Currently, all three operating systems have a roughly equal share of the network operating system market, which means that NetWare is still used in at least one-third of all server systems.
NetWare features
NetWare offers the following features :

  • Multiprocessor kernel: This feature enables one NetWare operating system to utilize multiple processors. This process is called symmetric multiprocessing (SMP). SMP enables processors to share memory and bus paths, even coordinating the processing of a single application in parallel.
  • NLMs: Where UNIX uses daemons and Windows uses services, NetWare uses NetWare Loadable Modules (or NLMs) to provide services from the server. NLMs are programs that run in the background on the server to provide consistent services to the network.
  • PCI Hot Plug: This feature enables administrators to dynamically configure PCI network components while the system is running. You can replace, upgrade, or add new cards with the Hot replace, Hot upgrade, and Hot expansion features, respectively.

Client Support
NetWare 5 comes with Novell Client software for three client platforms: DOS and Windows 3.1x, Windows 95/98, and Windows NT.

Interoperability
You can set the Novell Clients for Windows 95/98 and Windows NT to work with one of three network protocol options: IP only, IP and IPX, or IPX only.

Authentication
Centralized login authentication

File and Print Services
File Services NetWare offers two choices of mutually compatible file services: Novell Storage Services (NSS) and the traditional NetWare File System. Both kinds of file services let you store, organize, manage, access, and retrieve data on the network. NSS gathers all unpartitioned free space that exists on all the hard drives connected to your server, together with any unused space in NetWare volumes, and places it into a storage pool. You create NSS volumes from this storage pool during server installation or later through NWCONFIG. Novell Distributed Print Services (NDPS) is the default and preferred print system in NetWare. NDPS supports IP-based as well as IPX-based printing.

Security
Novell has support for a public key infrastructure built into NetWare 5 using a public certificate, developed by RSA Security.

Windows

Directory Services
A directory service is a database of user accounts and other information that network administrators use to control access to shared network resources. When users connect to a network, they have to be authenticated before they can access network resources. Authentication is the process of checking the user\’s credentials (usually a user name and a password) against the directory. Users that supply the proper credentials are permitted access according to the permissions specified by the network administrator.

Client Support
Windows 3.x, Windows 95, Windows 98, and Windows NT Workstation 4.0 Windows 2000 Professional, Xp Pro. Vista Ultimate, Vista Business.

Interoperability
Windows 2000,2003,2008 Server supports UNIX, Novell NetWare, Windows NT Server 4.0, and Macintosh.

Authentication
Successful user authentication in a Windows 2000,2003,2008 computing environment consists of separate processes: interactive logon, which confirms the user\’s identification to either a domain account or a local computer, and network authentication, which confirms the user\’s identification to any network service that the user attempts to access.

Types of authentication
Kerberos V5 is used with either a password or a smart card for interactive logon. It is also the default method of network authentication for services.The Kerberos V5 protocol verifies both the identity of the user and network services Secure Socket Layer/Transport Layer Security (SSL/TLS) authentication, is used when a user attempts to access a secure Web server.

File and Print Services
You can add and maintain printers in Windows server using the print administration wizard, and you can add file shares using Active Directory management tools. Windows server also offers Distributed File Services, which let you combine files on more than one server into a single share.

Active Directory
After many years of anticipation, Microsoft introduced an enterprise directory service in the Windows 2000 Server product line, called Active Directory. It uses a hierarchical tree design comprised of container and leaf objects. The fundamental unit of organization in Active Directory directory service is the domain, but; you can group domains together into a tree, and even group multiple trees together into a forest. Domains that are in the same tree automatically have bidirectional trust relationships established between them, which eliminates the need for administrators to create them manually. The trust relationships are also transitive , meaning that if Domain A trusts Domain B and Domain B trusts Domain C, then Domain A trusts Domain C.

Security
User-level security protects shared network resources by requiring that a security provider authenticate a user’s request to access resources. The domain controller , grants access to the shared resource by verifying that the user name and password are the same as those on the user account list stored on the network security provider. Because the security provider maintains a network-wide list of user accounts and passwords, each client computer does not have to store a list of accounts. Share-level security protects shared network resources on the computer with individually assigned passwords. For example, you can assign a password to a folder or a locally attached printer. If other users want to access it, they need to type in the appropriate password. If you do not assign a password to a shared resource, every user with access to the network can access that resource.

Appleshare IP (Internet Protocol)

Client Support
TCP/IP file sharing with Macintosh clients using Network File System (NFS), and File Transfer Apple File Protocol 3.0.

Interoperability
Windows Server Message Block (SMB) file sharing.

File and Print Services
File Services:

  • Apple Filing Protocol (AFP) over TCP/IP and AppleTalk
  • Server Message Block (SMB) over TCP/IP
  • File Transfer Protocol (FTP) over TCP/IP

Print Services:

  • PAP (AppleTalk)
  • LPR/LPD

Application Support

  • HTTP
  • Mail (SMTP, POP, IMAP and Authenticated Post Office Protocol APOP)
  • Mac CGI

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Basic Networking Commands Explained with Examples

This tutorial explains basic networking commands (such as tracert, traceroute, ping, arp, netstat, nbstat, NetBIOS, ipconfig, winipcfg and nslookup) and their arguments, options and parameters in details including how they are used to troubleshoot the computer network.

Tracert / traceroute

Tracert: Determines the path taken to a destination by sending Internet Control Message Protocol (ICMP) Echo Request messages to the destination with incrementally increasing Time to Live (TTL) field values. The path displayed is the list of near-side router interfaces of the routers in the path between a source host and a destination. The near-side interface is the interface of the router that is closest to the sending host in the path. Used without parameters, tracert displays help.
This diagnostic tool determines the path taken to a destination by sending ICMP Echo Request messages with varying Time to Live (TTL) values to the destination. Each router along the path is required to decrement the TTL in an IP packet by at least 1 before forwarding it.

Effectively, the TTL is a maximum link counter. When the TTL on a packet reaches 0, the router is expected to return an ICMP Time Exceeded message to the source computer. Tracert determines the path by sending the first Echo Request message with a TTL of 1 and incrementing the TTL by 1 on each subsequent transmission until the target responds or the maximum number of hops is reached. The maximum number of hops is 30 by default and can be specified using the -h parameter.

The path is determined by examining the ICMP Time Exceeded messages returned by intermediate routers and the Echo Reply message returned by the destination. However, some routers do not return Time Exceeded messages for packets with expired TTL values and are invisible to the tracert command. In this case, a row of asterisks (*) is displayed for that hop.

Examples:

To trace the path to the host named www.google.co.in use following command

 tracert www.google.co.in
 

To trace the path to the host named www.google.com and prevent the resolution of each IP address to its name, type:
tracert -d www.google.com

To trace the path to the host named www.google.com and use the loose source route 10.12.0.1-10.29.3.1-10.1.44.1, type:
tracert -j 10.12.0.1 10.29.3.1 10.1.44.1 www.google.com

Syntax

tracert [-d] [-h MaximumHops] [-j HostList] [-w Timeout] [TargetName]



Parameters

-d Prevents tracert from attempting to resolve the IP addresses of intermediate routers to their names. This can speed up the display of tracert results.
-h MaximumHops Specifies the maximum number of hops in the path to search for the target (destination). The default is 30 hops.
-j HostList Specifies that Echo Request messages use the Loose Source Route option in the IP header with the set of intermediate destinations specified in HostList. With loose source routing, successive intermediate destinations can be separated by one or multiple routers. The maximum number of addresses or names in the host list is 9. The HostList is a series of IP addresses (in dotted decimal notation) separated by spaces.
-w Timeout Specifies the amount of time in milliseconds to wait for the ICMP Time Exceeded or Echo Reply message corresponding to a given Echo Request message to be received. If not received within the time-out, an asterisk (*) is displayed. The default time-out is 4000 (4 seconds).

Ping

Verifies IP-level connectivity to another TCP/IP computer by sending Internet Control Message Protocol (ICMP) Echo Request messages. The receipt of corresponding Echo Reply messages are displayed, along with round-trip times. Ping is the primary TCP/IP command used to troubleshoot connectivity, reachability, and name resolution.

You can use ping to test both the computer name and the IP address of the computer. If pinging the IP address is successful, but pinging the computer name is not, you might have a name resolution problem. In this case, ensure that the computer name you are specifying can be resolved through the local Hosts file, by using Domain Name System (DNS) queries, or through NetBIOS name resolution techniques.
To test a TCP/IP configuration by using the ping command:

  • To quickly obtain the TCP/IP configuration of a computer, open Command Prompt, and then type ipconfig . From the display of the ipconfig command, ensure that the network adapter for the TCP/IP configuration you are testing is not in a Media disconnected state.
  • At the command prompt, ping the loopback address by typing ping 127.0.0.1
  • Ping the IP address of the computer.
  • Ping the IP address of the default gateway. If the ping command fails, verify that the default gateway IP address is correct and that the gateway (router) is operational.
  • Ping the IP address of a remote host (a host that is on a different subnet). If the ping command fails, verify that the remote host IP address is correct, that the remote host is operational, and that all of the gateways (routers) between this computer and the remote host are operational.
  • Ping the IP address of the DNS server. If the ping command fails, verify that the DNS server IP address is correct, that the DNS server is operational, and that all of the gateways (routers) between this computer and the DNS server are operational.



Arp

Displays and modifies entries in the Address Resolution Protocol (ARP) cache, which contains one or more tables that are used to store IP addresses and their resolved Ethernet or Token Ring physical addresses. There is a separate table for each Ethernet or Token Ring network adapter installed on your computer.

Syntax

arp [-a [InetAddr] [-N IfaceAddr]] [-g [InetAddr] [-N IfaceAddr]] [-d InetAddr [IfaceAddr]] [-s InetAddr EtherAddr [IfaceAddr]]

Parameters

Used without parameters displays help
-a [InetAddr] [-N IfaceAddr] Displays current ARP cache tables for all interfaces. To display the ARP cache entry for a specific IP address, use arp -a with the InetAddr parameter, where InetAddr is an IP address. To display the ARP cache table for a specific interface, use the -N IfaceAddr parameter where IfaceAddr is the IP address assigned to the interface. The -N parameter is case-sensitive.
-g [InetAddr] [-N IfaceAddr] Identical to -a.
-d InetAddr [IfaceAddr] Deletes an entry with a specific IP address, where InetAddr is the IP address. To delete an entry in a table for a specific interface, use the IfaceAddr parameter where IfaceAddr is the IP address assigned to the interface. To delete all entries, use the asterisk (*) wildcard character in place of InetAddr.
-s InetAddr EtherAddr [IfaceAddr] Adds a static entry to the ARP cache that resolves the IP address InetAddr to the physical address EtherAddr. To add a static ARP cache entry to the table for a specific interface, use the IfaceAddr parameter where IfaceAddr is an IP address assigned to the interface.

Examples:

To display the ARP cache tables for all interfaces use following command

 arp -a

To display the ARP cache table for the interface that is assigned the IP address 192.168.42.171

Netstat

Displays active TCP connections, ports on which the computer is listening, Ethernet statistics, the IP routing table,
IPv4 statistics (for the IP, ICMP, TCP, and UDP protocols), and IPv6 statistics (for the IPv6, ICMPv6, TCP over IPv6, and UDP over IPv6 protocols).

Netstat provides statistics for the following:

  • Proto – The name of the protocol (TCP or UDP).
  • Local Address – The IP address of the local computer and the port number being used. The name of the local computer that corresponds to the IP address and the name of the port is shown unless the -n parameter is specified. If the port is not yet established, the port number is shown as an asterisk (*).
  • Foreign Address – The IP address and port number of the remote computer to which the socket is connected. The names that corresponds to the IP address and the port are shown unless the -n parameter is specified. If the port is not yet established, the port number is shown as an asterisk (*).

(state) Indicates the state of a TCP connection. The possible states are as follows:

  • CLOSE_WAIT
  • CLOSED
  • ESTABLISHED
  • FIN_WAIT_1
  • FIN_WAIT_2
  • LAST_ACK
  • LISTEN
  • SYN_RECEIVED
  • SYN_SEND
  • TIMED_WAIT

Syntax

netstat [-a] [-e] [-n] [-o] [-p Protocol] [-r] [-s] [Interval]

Parameters

Used without parameters displays active TCP connections.
-a Displays all active TCP connections and the TCP and UDP ports on which the computer is listening.
-e Displays Ethernet statistics, such as the number of bytes and packets sent and received. This parameter can be combined with -s.
-n Displays active TCP connections, however, addresses and port numbers are expressed numerically and no attempt is made to determine names.
-o Displays active TCP connections and includes the process ID (PID) for each connection. You can find the application based on the PID on the Processes tab in Windows Task Manager. This parameter can be combined with -a, -n, and -p.
-p Shows connections for the protocol specified by Protocol. In this case, the Protocol can be tcp, udp, tcpv6, or udpv6. If this parameter is used with -s to display statistics by protocol, Protocol can be tcp, udp, icmp, ip, tcpv6, udpv6, icmpv6, or ipv6.
-s Displays statistics by protocol. By default, statistics are shown for the TCP, UDP, ICMP, and IP protocols. If the IPv6 protocol for Windows XP is installed, statistics are shown for the TCP over IPv6, UDP over IPv6, ICMPv6, and IPv6 protocols. The -p parameter can be used to specify a set of protocols.
-r Displays the contents of the IP routing table. This is equivalent to the route print command.
Interval Redisplays the selected information every Interval seconds. Press CTRL+C to stop the redisplay. If this parameter is omitted, netstat prints the selected information only once.
/? – Displays help at the command prompt.

Nbtstat

Displays NetBIOS over TCP/IP (NetBT) protocol statistics

NetBIOS name tables for both the local computer and remote computers, and the NetBIOS name cache. Nbtstat allows a refresh of the NetBIOS name cache and the names registered with Windows Internet Name Service (WINS).

Nbtstat command-line parameters are case-sensitive.

Syntax

nbtstat [-a RemoteName] [-A IPAddress] [-c] [-n] [-r] [-R] [-RR] [-s] [-S] [Interval]

Parameters

Used without parameters displays help.
-a RemoteName Displays the NetBIOS name table of a remote computer, where RemoteName is the NetBIOS computer name of the remote computer. The NetBIOS name table is the list of NetBIOS names that corresponds to NetBIOS applications running on that computer.
-A IPAddress Displays the NetBIOS name table of a remote computer, specified by the IP address (in dotted decimal notation) of the remote computer.
-c Displays the contents of the NetBIOS name cache, the table of NetBIOS names and their resolved IP addresses.
-n Displays the NetBIOS name table of the local computer. The status of Registered indicates that the name is registered either by broadcast or with a WINS server.
-r Displays NetBIOS name resolution statistics. On a Windows XP computer that is configured to use WINS, this parameter returns the number of names that have been resolved and registered using broadcast and WINS.
-R Purges the contents of the NetBIOS name cache and then reloads the #PRE-tagged entries from the Lmhosts file.
-RR Releases and then refreshes NetBIOS names for the local computer that is registered with WINS servers.
-s Displays NetBIOS client and server sessions, attempting to convert the destination IP address to a name.
-S Displays NetBIOS client and server sessions, listing the remote computers by destination IP address only.
Interval Redisplays selected statistics, pausing the number of seconds specified in Interval between each display. Press CTRL+C to stop redisplaying statistics. If this parameter is omitted, nbtstat prints the current configuration information only once.
/? – Displays help at the command prompt.

Ipconfig

Displays all current TCP/IP network configuration values and refreshes Dynamic Host Configuration Protocol (DHCP) and Domain Name System (DNS) settings. This command is most useful on computers that are configured to obtain an IP address automatically. This enables users to determine which TCP/IP configuration values have been configured by DHCP, Automatic Private IP Addressing (APIPA), or an alternate configuration.

  • If the Adapter name contains any spaces, use quotation marks around the adapter name (that is, \”Adapter Name\”).
  • For adapter names, ipconfig supports the use of the asterisk (*) wildcard character to specify either adapters with names that begin with a specified string or adapters with names that contain a specified string.
  • For example, Local* matches all adapters that start with the string Local and *Con* matches all adapters that contain the string Con.

Syntax

ipconfig [/all] [/renew [Adapter]] [/release [Adapter]] [/flushdns] [/displaydns] [/registerdns] [/showclassid Adapter] [/setclassid Adapter [ClassID]]

Parameters

Used without parameters displays the IP address, subnet mask, and default gateway for all adapters.
/all Displays the full TCP/IP configuration for all adapters. Without this parameter, ipconfig displays only the IP address, subnet mask, and default gateway values for each adapter. Adapters can represent physical interfaces, such as installed network adapters, or logical interfaces, such as dial-up connections.
/renew [Adapter] Renews DHCP configuration for all adapters (if an adapter is not specified) or for a specific adapter if the Adapter parameter is included. This parameter is available only on computers with adapters that are configured to obtain an IP address automatically. To specify an adapter name, type the adapter name that appears when you use ipconfig without parameters.
/release [Adapter] Sends a DHCPRELEASE message to the DHCP server to release the current DHCP configuration and discard the IP address configuration for either all adapters (if an adapter is not specified) or for a specific adapter if the Adapter parameter is included. This parameter disables TCP/IP for adapters configured to obtain an IP address automatically. To specify an adapter name, type the adapter name that appears when you use ipconfig without parameters.
/flushdns Flushes and resets the contents of the DNS client resolver cache. During DNS troubleshooting, you can use this procedure to discard negative cache entries from the cache, as well as any other entries that have been added dynamically.
/displaydns Displays the contents of the DNS client resolver cache, which includes both entries preloaded from the local Hosts file and any recently obtained resource records for name queries resolved by the computer. The DNS Client service uses this information to resolve frequently queried names quickly, before querying its configured DNS servers.
/registerdns Initiates manual dynamic registration for the DNS names and IP addresses that are configured at a computer. You can use this parameter to troubleshoot a failed DNS name registration or resolve a dynamic update problem between a client and the DNS server without rebooting the client computer. The DNS settings in the advanced properties of the TCP/IP protocol determine which names are registered in DNS.
/showclassid Adapter Displays the DHCP class ID for a specified adapter. To see the DHCP class ID for all adapters, use the asterisk (*) wildcard character in place of Adapter. This parameter is available only on computers with adapters that are configured to obtain an IP address automatically.
/setclassid Adapter [ClassID] Configures the DHCP class ID for a specified adapter. To set the DHCP class ID for all adapters, use the asterisk (*) wildcard character in place of Adapter. This parameter is available only on computers with adapters that are configured to obtain an IP address automatically. If a DHCP class ID is not specified, the current class ID is removed.

Examples:

ipconfig To display the basic TCP/IP configuration for all adapters
ipconfig /all To display the full TCP/IP configuration for all adapters
ipconfig /renew \”Local Area Connection\” To renew a DHCP-assigned IP address configuration for only the Local Area Connection adapter
ipconfig /flushdns To flush the DNS resolver cache when troubleshooting DNS name resolution problems
ipconfig /showclassid Local To display the DHCP class ID for all adapters with names that start with Local
ipconfig /setclassid \”Local Area Connection\” TEST To set the DHCP class ID for the Local Area Connection adapter to TEST

winipcfg

This utility allows users or adminstrators to see the current IP address and other useful information about your network configuration. You can reset one or more IP addresses. The Release or Renew buttons allow you to release or renew one IP address. If you want to release or renew all IP addresses click Release All or Renew All. When one of these buttons is clicked, a new IP address is obtained from either the DHCP service or from the computer assigning itself an automatic private IP address. To use the winipcfg utility:

  • Click Start,and then click Run and type winipcfg
  • Click More Info.
  • To see the addresses of the DNS servers the computer is configured to use, click the ellipsis (…) button to the right of DNS Servers.
  • To see address information for your network adapter(s), select an adapter from the list in Ethernet Adapter Information.

nslookup

Nslookup (Name Server lookup) is a UNIX shell command to query Internet domain name servers.

Definitions

  • Nameserver: These are the servers that the internet uses to find out more about the domain. Usually they are an ISP\’s computer.
  • Mailserver: Where email is sent to.
  • Webserver: The domains website.
  • FTPserver: FTP is file transfer protocol, this server is where files may be stored.
  • Hostname: The name of the host as given by the domain.
  • Real Hostname: This is hostname that you get by reverse resolving the IP address, may be different to the given hostname.
  • IP Address: Unique four numbered identifier that is obtained by resolving the hostname.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

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Networking Tutorials

Network Security Types, Terms and Definitions Explained

This tutorial presents a collection of network security types, terms and definitions. This network security terminology collection will help you in learning the basic concepts of network security in computer network with possible security threats and solutions.

Port Blocking / Filtering

A network layer firewall works as a packet filter by deciding what packets will pass the firewall according to rules defined by the administrator. Filtering rules can act on the basis of source and destination address and on ports, in addition to whatever higher-level network protocols the packet contains. Network layer firewalls tend to operate very fast, and transparently to users. Network layer firewalls generally fall into two sub-categories, stateful and stateless. Stateful firewalls hold some information on the state of connections (for example: established or not, initiation, handshaking, data or breaking down the connection) as part of their rules (e.g. only hosts inside the firewall can establish connections on a certain port).

Stateless firewalls have packet-filtering capabilities but cannot make more complex decisions on what stage communications between hosts have reached. Stateless firewalls therefore offer less security. Stateless firewalls somewhat resemble a router in their ability to filter packets.

Any normal computer running an operating system which supports packet filtering and routing can function as a network layer firewall. Appropriate operating systems for such a configuration include Linux, Solaris, BSDs or Windows Server.

Authentication

The process of identifying an individual, usually based on a username and password. In security systems, authentication is distinct from authorization , which is the process of giving individuals access to system objects based on their identity. Authentication merely ensures that the individual is who he or she claims to be, but says nothing about the access rights of the individual.

Encryption

Encryption is part of a larger process of encoding and decoding messages to keep information secure. This process, though commonly called encryption, is more correctly called cryptography, is the use of mathematical transformations to protect data. Cryptography is primarily a software-based solution and, in most cases, should not include significant hardware costs. It is a key tool in protecting privacy as it allows only authorized parties to view the data. Encryption is also used to ensure data integrity, as it protects data from being modified or corrupted.

VLANs (Virtual Local Area Networks).

A virtual LAN (VLAN) is a logical grouping of network devices in the same broadcast domain that can span multiple physical segments.A VLAN is a group of devices in the same broadcast domain or subnet. VLANs are good at logically separating traffic between different groups of users. VLANs contain/isolate broadcast traffic, where you need a router to move traffic between VLANs.

Logically speaking, VLANs are subnets. A subnet, or a network, is a contained broadcast domain. A broadcast that occurs in one subnet will not be forwarded, by default, to another subnet.

Routers, or layer 3 devices, provide this boundary function. Each of these subnets requires a unique network number. And to move from one network number to another, you need a router. In the case of broadcast domains and switches, each of these separate broadcast domains is a separate VLAN; therefore, you still need a routing function to move traffic between different VLANs.

Extranets



An extranet is a private network that uses Internet protocols, network connectivity, to securely share part of an organization\’s information or operations with suppliers, vendors, partners, customers or other businesses. An extranet can be viewed as part of a company\’s Intranet that is extended to users outside the company normally over the Internet. An extranet requires security and privacy. These can include firewalls, server management, the issuance and use of digital certificates or similar means of user authentication, encryption of messages, and the use of virtual private networks (VPNs) that tunnel through the public network.
Advantages

  • Extranets can improve organization productivity by automating processes that were previously done manually.
  • Extranets allow organization or project information to be viewed at times convenient for business partners, customers, employees, suppliers and other stake-holders.
  • Information on an extranet can be updated, edited and changed instantly. All authorised users therefore have immediate access to the most up-to-date information.

Disadvantages

  • Extranets can be expensive to implement and maintain within an organisation
  • Security of extranets can be a big concern when dealing with valuable information.
  • Extranets can reduce personal contact (face-to-face meetings) with customers and business partners. This could cause a lack of connections made between people and a company

Intranet

Intranets differ from \”Extranets\” in that the former is generally restricted to employees of the organization while extranets can generally be accessed by customers, suppliers, or other approved parties. An intranet is a private computer network that uses Internet protocols, network connectivity, to securely share part of an organization\’s information or operations with its employees. Sometimes the term refers only to the most visible service, the internal website. The same concepts and technologies of the Internet such as clients and servers running on the Internet protocol suite are used to build an intranet. HTTP and other Internet protocols are commonly used as well, especially FTP and e-mail.

Antivirus Software.

Antivirus software consists of computer programs that attempt to identify, thwart and eliminate computer viruses and other malicious software. Antivirus software typically uses two different techniques to accomplish this:

  • Examining files to look for known viruses matching definitions in a virus dictionary
  • Identifying suspicious behavior from any computer program which might indicate infection. Such analysis may include data captures, port monitoring and other methods.

Most commercial antivirus software uses both of these approaches, with an emphasis on the virus dictionary approach.

Dictionary Approach:
When the antivirus software looks at a file, it refers to a dictionary of known viruses that the authors of the antivirus software have identified. If a piece of code in the file matches any virus identified in the dictionary, then the antivirus software can take one of the following actions:

  • attempt to repair the file by removing the virus itself from the file
  • quarantine the file
  • delete the infected file.

Suspicious Behavior Approach:
Unlike the dictionary approach, the suspicious behavior approach therefore provides protection against brand-new viruses that do not yet exist in any virus dictionaries. Most antivirus software are not using this approach much today. Using this approach the antivirus software:

  • Doesn\’t attempt to identify known viruses
  • Monitors the behavior of all programs.
  • If one program tries to write data to an executable program, the antivirus software can flag this suspicious behavior
  • alert a user and ask what to do.

Analysis Approach:

  • Antivirus software could try to emulate the beginning of the code of each new executable that the system invokes before transferring control to that executable.
  • If the program seems to use self-modifying code or otherwise appears as a virus, one could assume that a virus has infected the executable. However, this method could result in a lot of false positives.

Fault Tolerance:

Fault tolerance is the ability of a system to continue functioning when part of the system fails. Normally, fault tolerance is used in describing disk subsystems, but it can also apply to other parts of the system or the entire system. Fully fault-tolerant systems use redundant disk controllers and power supplies as well as fault-tolerant disk subsystems. You can also use an uninterruptible power supply (UPS) to safeguard against local power failure. Although the data is always available in a fault-tolerant system, you still need to make backups that are stored offsite to protect the data against disasters such as a fire.

Network Redundancy

Service interruptions on a network are not always the result of a computer or drive failure. Sometimes the network itself is to blame. For this reason, many larger internetworks are designed with redundant components that enable traffic to reach a given destination in more than one way. If a network cable is cut or broken, or if a router or switch fails, redundant equipment enables data to take another path to its destination. There are several ways to provide redundant paths. Typically, you have at least two routers or switches connected to each network, so that the computers can use either one as a gateway to the other segments. Example, you can build a network with two backbones. Each workstation can use either of the routers on its local segment as a gateway. You can also use this arrangement to balance the traffic on the two backbones by configuring half of the computers on each local area network (LAN) to use one of the routers as its default gateway and the other half to use the other router.

Storage

A redundant array of independent disks (RAID) is an example of a fault-tolerant storage device that uses data redundancy.

RAID

Redundant Array of Inexpensive (or Independent) Disks. A RAID array is a collection of drives which collectively act as a single storage system, which can tolerate the failure of a drive without losing data, and which can operate independently of each other.



Level 0
Referred to as striping, is not redundant. Data is split across drives, resulting in higher data throughput. Since no redundant information is stored, performance is very good, but the failure of any disk in the array results in all data loss.

Level 1
Referred to as mirroring with 2 hard drives. It provides redundancy by duplicating all data from one drive on another drive. Performance is better than a single drive, but if either drive fails, no data is lost. This is a good entry-level redundant system, since only two drives are required.

Level 2
Which uses Hamming error correction codes, is intended for use with drives which do not have built-in error detection. All SCSI drives support built-in error detection, so this level is not needed if using SCSI drives.

Level 3
Stripes data at a byte level across several drives, with parity stored on one drive. It is otherwise similar to level 4. Byte-level striping requires hardware support for efficient use.

Level 4
Stripes data at a block level across several drives, with parity stored on one drive. The parity information allows recovery from the failure of any single drive. Performance is very good for reads. Writes, however, require that parity data be updated each time. This slows small random writes, in particular, though large writes or sequential writes are fairly fast.

Level 5
Striping with distributed parity. Similar to level 4, but distributes parity among the drives. No single disk is devoted to parity. This can speed small writes in multiprocessing systems. Because parity data must be distributed on each drive during reads, the performance for reads tends to be considerably lower than a level 4 array.

Disaster recovery

Disaster recovery

Fault Tolerance

Most people think about disaster recovery in terms of restoration of the damaged network, but it’s actually less expensive to prevent a disaster than to restore one.

Fault tolerance is another term for redundancy. You can have redundant components within a server, redundant servers, and even redundant networks, in the case of a hot site. A fault-tolerant system simply has a spare part that takes over if another part fails. Fault tolerance can work for the following:

Memory

Some servers support error-correcting memory with a spare memory module to use in case of memory failure.

Network interface cards (NICs).

NICs can be redundant in two ways. They can share the network traffic, or one of the NICs can wait until the first fails before it kicks in.
Redundant Array of Inexpensive Disks (RAID).
Data is mirrored, shared, or striped across multiple disks. Pay attention to these versions of RAID:

RAID 1:
Mirroring disks connected to a single hard disk controller, or duplexing disks connected to two different hard disk controllers.

RAID 5:
A group of three or more disks is combined into a volume with the disk striped across the disks, and parity is used to ensure that if any one of the disks fails, the remaining disks will still have all data available.

Power supplies.
One power supply takes over if the original fails.

Clusters.
Two or more servers are grouped to provide services as if the group were a single server. A cluster is transparent to end users. Usually, a server member of a cluster can take over for a failed partner with no impact on the network.

Backup / restore

Offsite storage
A remote backup service, online backup service or managed backup service is a service that provides users with an online system for backing up and storing computer files. Managed backup providers are companies that have the software and server space for storing files.

Hot and cold spares

  • A hot spare disk is running, ready to start working in the case of a failure.
  • A cold spare disk is not running.

A hot spare is used as a failover mechanism to provide reliability in system configurations. The hot spare is active and connected as part of a working system. When a key component fails, the hot spare is switched into operation. Examples of hot spares are components such as networked printers, and hard disks. The equipment is powered on, or considered \”hot\”, but not actively functioning in the system. In the case of a disk drive, data is being mirrored so when the hot spare takes over, the system continues to operate with minimal or no downtime.

Hot Spare Disk
is a disk or group of disks used to automatically or manually, replace a failing or failed disk in a RAID configuration. The hot spare disk reduces the mean time to recovery (MTTR) for the RAID redundancy group, thus reducing the probability of a second disk failure and the resultant data loss that would occur in any singly redundant RAID (e.g., RAID-1, RAID-5, RAID-10).

Hot, warm and cold sites

A backup site is a location where a business can easily relocate following a disaster, such as fire, flood. There are three types of backup sites, including cold sites, warm sites, and hot sites. The differences between the types are determined by the costs and effort required to implement each.

Hot Site is a duplicate of the original site of the business, with full computer systems as well as near-complete backups of user data. Following a disaster, the hot site exists so that the business can relocate with minimal losses to normal operations. Ideally, a hot site will be up and running within a matter of hours. This type of backup site is the most expensive to operate.

Warm Site is a location where the business can relocate to after the disaster that is already stocked with computer hardware similar to that of the original site, but does not contain backed up copies of data and information.

Cold Site is the most inexpensive type of backup site for a business to operate. It does not include backed up copies of data and information from the its original location, nor does it include hardware already set up. The lack of hardware contributes to the minimal startup costs of the cold site, but requires additional time following the disaster to have the operation running at a capacity close to that prior to the disaster.

Security protocols protect a computer from attacks. To understand how security protocols work, you must first understand what types of attacks they protect against. Networks and data are vulnerable to both active attacks, in which information is altered or destroyed, and passive attacks, in which information is monitored. Attacks that you might encounter include the following:

Altering data

This active attack takes place when data is interrupted in transit and modified before it reaches its destination, or when stored data is altered. This passive attack takes advantage of network traffic that is transmitted across the wire in clear text. The attacker simply uses a device that monitors traffic and \”listens in\” to discover information. You\’ll hear this term referred to as sniffing the wire, and sometimes as snooping.

IP address spoofing

One way to authenticate data is to check the IP address in data packets. If the IP address is valid, that data is allowed to pass into the private network. IP address spoofing is the process of changing the IP address so that data packets will be accepted. IP address spoofing can be used to modify or delete data, or to perpetuate an additional type of attack.

Password pilfering

A hacker will obtain user IDs and passwords, or even encryption keys, to gain access to network data, which can then be altered, deleted, or even used to create another attack. This type of attack is usually done by asking unsuspecting users, reading sticky notes containing passwords that are posted next to computers, or sniffing the wire for password information. Sometimes a hacker will attempt to get hired at a company merely to obtain an ID and password with access rights to the network.

Denial of service

This active attack is intended to cause full or partial network outages so that people will not be able to use network resources and productivity will be affected. The attacker floods so many packets through the network or through specific resources that other users can\’t access those resources. The denial-of-service attack can also serve as a diversion while the hacker alters information or damages systems.

Virus

A virus is an attack on a system. It is a piece of software code that is buried inside a trusted application (or even an e-mail message) that invokes some action to wreak havoc on the computer or other network resources.

Security Method Type of Attack Notes
Authentication Password guessing attacks Verifies the user\’s identity
Access control Password pilfering Protects sensitive data from access by the average user
Encryption Data alteration Prevents the content of the packets from being tampered with
Certificates Eavesdropping Transmits identity information securely
Firewalls Denial of service (as well as others) When configured correctly, can prevent many denial-of-service attacks
Signatures Data alteration Protects stored data from tampering
Public key infrastructure Spoofing Ensures that data received is from correct sender
Code authentication Virus and other code attacks Protects the computer from altered executables
Physical security Password pilfering Protects unauthorized persons from having access to authorized users and their IDs and passwords
Password policies Password pilfering Ensures that passwords are difficult to guess or otherwise decipher

IPSec (Internet Protocol Security)

IPSec Is a set of protocols used to support secure exchange of packets at the IP layer. IPsec supports two encryption modes: Transport and Tunnel.

Transport mode encrypts only the data portion of each packet, but leaves the header untouched.

The more secure Tunnel mode encrypts both the header and the data portion.

For IPsec to work, the sending and receiving devices must share a public key. This is accomplished through a protocol known as Internet Security Association and Key Management Protocol/Oakley, which allows the receiver to obtain a public key and authenticate the sender using digital certificates. IPsec protocols operate at the network layer, layer 3 of the OSI model. Other Internet security protocols in widespread use, such as SSL and TLS, operate from the transport layer up (OSI layers 4 – 7). This makes IPsec more flexible, as it can be used for protecting both TCP and UDP based protocols

L2TP (Layer 2 Tunneling Protocol)

Layer 2 Tunneling Protocol is a tunneling protocol used to support virtual private networks VPNs. L2TP is an extension to the PPP protocol that enables ISPs to operate Virtual Private Networks. L2TP combines the best features of two other tunneling protocols:PPTP from Microsoft and L2F from Cisco Systems.

SSL (Secure Sockets Layer)

Secure Sockets Layer is a protocol that supplies secure data communication through data encryption and decryption. SSL enables communications privacy over networks by using a combination of public key, and bulk data encryption.

WEP (Wired Equivalent Privacy)

Wired Equivalent Privacy is a scheme that is part of the IEEE 802.11 wireless networking standard to secure IEEE 802.11 wireless networks. Because a wireless network broadcasts messages using radio, it is particularly susceptible to eavesdropping.
WEP was intended to provide comparable confidentiality to a traditional wired network and thus it does not protect users of the network from each other.

WPA (Wi-Fi Protected Access)

A security protocol for wireless networks that builds on the basic foundations of WEP. It secures wireless data transmission by using a key similar to WEP, but the added strength of WPA is that the key changes dynamically. The changing key makes it much more difficult for a hacker to learn the key and gain access to the network.

WPA2 (Wi-Fi Protected Access 2)

WPA2 is the second generation of WPA security and provides a stronger encryption mechanism through Advanced Encryption Standard (AES), which is a requirement for some government users.

802.11x

IEEE 802.11 also known by the brand Wi-Fi, denotes a set of Wireless LAN/WLAN standards developed by working group 11 of the IEEE LAN/MAN Standards Committee (IEEE 802). The term 802.11x is also used to denote this set of standards and is not to be mistaken for any one of its elements. There is no single 802.11x standard.

Protocol Release Date Op. Frequency Data Rate (Typ) Data Rate (Max) Range (Indoor) Range (Outdoor)
802.11a 1999 5.15-5.35/5.47-5.725/5.725-5.875 GHz 25 Mbit/s 54 Mbit/s ~25 meters ~75 meters
802.11b 1999 2.4-2.5 GHz 6.5 Mbit/s 11 Mbit/s ~35 meters ~100 meters
802.11g 2003 2.4-2.5 GHz 25 Mbit/s 54 Mbit/s ~25 meters ~75 meters
802.11n 2007 2.4 GHz or 5 GHz bands 200 Mbit/s 540 Mbit/s ~50 meters ~125 meters

Identify authentication protocols:

CHAP (Challenge Handshake Authentication Protocol)

Challenge Handshake Authentication Protocol is a challenge-response authentication protocol that uses the industry-standard Message Digest 5 (MD5) hashing scheme to encrypt the response. CHAP is used by various vendors of network access servers and clients.

MS-CHAP (Microsoft Challenge Handshake Authentication Protocol)

MS-CHAP Microsoft Challenge Handshake Authentication Protocol. MS-CHAP is a nonreversible, encrypted password authentication protocol. The challenge handshake process works as follows:

  • The remote access server or the IAS server sends a challenge to the remote access client that consists of a session identifier and an arbitrary challenge string.
  • The remote access client sends a response that contains the user name and a nonreversible encryption of the challenge string, the session identifier, and the password.
  • The authenticator checks the response and, if valid, the user\’s credentials are authenticated.

PAP (Password Authentication Protocol)

Password Authentication Protocol uses plaintext passwords and is the least sophisticated authentication protocol. It is typically negotiated if the remote access client and remote access server cannot negotiate a more secure form of validation.

RADIUS (Remote Authentication Dial-In User Service)

Is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. It is intended to work in both local and roaming situations.

Some ISPs (commonly modem, DSL, or wireless 802.11 services) require you to enter a username and password in order to connect on to the Internet. Before access to the network is granted, this information is passed to a Network Access Server (NAS) device over the Point-to-Point Protocol (PPP), then to a RADIUS server over the RADIUS protocol. The RADIUS server checks that the information is correct using authentication schemes like PAP, CHAP or EAP.

If accepted, the server will then authorize access to the ISP system and select an IP address. RADIUS is also widely used by VoIP service providers.

Kerberos and EAP (Extensible Authentication Protocol)).

An authentication system, Kerberos is designed to enable two parties to exchange private information across an open network. It works by assigning a unique key, called a ticket, to each user that logs on to the network. The ticket is then embedded in messages to identify the sender of the message.

Extensible Authentication Protocol, or EAP, is a universal authentication framework frequently used in wireless networks and Point-to-Point connections. Although the EAP protocol is not limited to wireless LANs and can be used for wired LAN authentication, it is most often used in wireless LANs. Recently, the WPA and WPA2 standard has officially adopted five EAP types as its official authentication mechanisms.

Smart Cards

Smart cards are gaining in popularity as a way to ensure secure authentication using a physical key. Smart cards are able to provide an interactive logon, secure e-mail messages, and authenticate access to network services.

Smart cards contain chips to store a user\’s private key and can also store logon information; public key certificates; and other information, depending on the smart card\’s usage. When a user needs to access a resource, the user inserts the smart card into a reader attached to the network. After typing in the user\’s personal identification number (PIN), the user is authenticated and can access network resources. The private key is automatically available for transparent access to encrypted information.

Smart cards require Public Key Infrastructure (PKI), a method of distributing encryption keys and certificates. In addition, each protected resource will require a smart-card reader. Some implementations of smart cards combine the smart card with employee badges so that employees need a single card for building and network access.

Remote access protocols and services:

RAS (Remote Access Service)

Remote Access Service A service that provides remote networking for telecommuters, mobile workers, and system administrators who monitor and manage servers at multiple branch offices. Users with RAS can dial in to remotely access their networks for services such as file and printer sharing, electronic mail, scheduling, and SQL database access.

PPP (Point-to-Point Protocol)

PPP is based on an open standard defined in RFCs 1332, 1661, and 2153. PPP works with asynchronous and synchronous serial connections as well as High-Speed Serial Interfaces (HSSI) and ISDN interfaces (BRI and PRI).

PPP Components
PPP has many more features than HDLC. Like HDLC, PPP defines a frame type and how two PPP devices communicate with each other, including the multiplexing of network and data link layer protocols across the same link. However, PPP also does the following:

  • Performs dynamic configuration of links
  • Allows for authentication
  • Compresses packet headers
  • Tests the quality of links
  • Performs error detection and correction
  • Allows multiple PPP physical connections to be bound together as a single logical connection (referred to as multilink)

PPP has three main components:

  • Frame format (encapsulation)
  • Link Control Protocol (LCP)
  • Network Control Protocol (NCP)

Each of these three components plays an important role in the setup, configuration, and transfer of information across a PPP connection.

SLIP (Serial Line Internet Protocol)

An older industry standard that is part of Windows remote access client to ensure interoperability with other remote access software.

PPPoE (Point-to-Point Protocol over Ethernet)

Point-to-Point Protocol over Ethernet encapsulates PPP frames in Ethernet frames and is usually used in conjunction with ADSL services.

It gives you a lot of the familiar PPP features like authentication, encryption, and compression, but there’s a downside—it has a lower maximum transmission unit (MTU) than standard Ethernet does, and if your firewall isn’t solidly configured, this little attribute can really give you some grief! Still somewhat popular in the United States, PPPoE on Ethernet’s.

main feature is that it adds a direct connection to Ethernet interfaces while providing DSL support as well. It’s often used by many hosts on a shared Ethernet interface for opening PPP sessions to various destinations via at least one bridging modem.

PPTP (Point-to-Point Tunneling Protocol)

Networking technology that supports multiprotocol virtual private networks (VPNs), enabling remote users to access corporate networks securely across the Internet or other networks by dialing into an Internet service provider (ISP) or by connecting directly to the Internet. The Point-to-Point Tunneling Protocol (PPTP) tunnels, or encapsulates, IP, IPX, or NetBEUI traffic inside of IP packets. This means that users can remotely run applications that are dependent upon particular network protocols.

VPN (Virtual Private Network)

Virtual private network A remote LAN that can be accessed through the Internet by using PPTP (see above)

RDP (Remote Desktop Protocol)

Remote Desktop Protocol (RDP) is a multi-channel protocol that allows a user to connect to a computer running Microsoft Terminal Services. Clients exist for most versions of Windows (including handheld versions), and other operating systems such as Linux, FreeBSD, Solaris Operating System and Mac OS X. The server listens by default on TCP port 3389.

  • Version 4.0 was introduced with Terminal Services in Windows NT 4.0 Server, Terminal Server Edition.
  • Version 5.0, introduced with Windows 2000 Server, added support for a number of features, including printing to local printers, and aimed to improve network bandwidth usage.
  • Version 5.1, introduced with Windows XP Professional, included support for 24-bit color and sound.
  • Version 5.2, introduced with Windows Server 2003, included support for console mode connections, a session directory, and local resource mapping.
  • Version, 6.0, introduced with Windows Vista and Windows Server includes a significant number of new features, most notably being able to remotely access a single application instead of the entire desktop, and support for 32 bit color.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

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Networking Tutorials

IP Address Classes and Definition Explained

This tutorial explains what IP address is, IP address format, types of IP address, IP address classes, subnet mask, private IP addresses and public IP addresses in detail with examples. Learn how IP address works and why an interface needs a unique IP address along with how to find the class of an IP address.

What is IP address?

An IP address is a numeric identity of an interface. Just like a postal address provides a unique identity to a house, an IP address provides a unique identity to an interface.

Why an interface needs unique IP address?

IP network uses IP address to find the destination interface and delivers the IP packets. In order to receive IP packets, an interface needs a unique IP address. If multiple interfaces have same IP address, IP network will not work.

Let’s understand it with an example. In a city all houses have same house number, suppose 195. If there is mail for house number 195, how mailman will delivery that mail? To deliver the mail at correct house, postal system needs unique address of that house. Exactly same way, to deliver an IP packet at correct interface, IP network needs a unique IP address of that interface.

How IP address works?



IP address works in IP network just like a postal address works in postal system. A postal address is the combination of two addresses, area address and house address. Area address is the group address of all houses which belong to a particular area and house address is the unique address of a specific house in that area. Each area is represented by a unique PIN code number in postal system.

PIN code helps in fast processing of mail. In a central post office where thousands or in some case millions of mail are received, forwarded and delivered daily, processing mail based on complete address is next to impossible. In a busy post office the clerk doesn’t read the complete address of a package to make his decision, he only pays attention on the PIN code. He reads the PIN code and drops the package in the container which will be forwarded to the nearest post office of the area which PIN code represents. Same process is used at next post office and so on and so on until the package reaches at the post office which delivers packages in destination area. At last post office, recipient’s house address is used to deliver the package.

Exact mechanism is used in IP network. An IP address is the combination of two addresses, network address and host address. Network address is the group address of all hosts which belong to a particular network and host address is the unique address of a specific host in that network.

Just like PIN code, network address helps in fast processing of the IP packets. In IP network, routers do exactly what post offices do in postal system. Routers use network address to find the destination network and host address to deliver the packets.

IP address format

An IP address is 32 bits in length. These bits are divided in four parts. Each part is known as octets and contains and 8 bits.

An IP address can be written in three notations; dotted-decimal, binary and hexadecimal. Among these types, dotted-decimal is the most popular and frequently used method for writing an IP address.

In dotted-decimal notation, each byte (8 bits) of the 32 bits IP address is written in decimal equivalent. The four resulting decimal numbers are separated by a dot and written in a sequence. 10.10.10.10, 172.168.10.1, 192.168.1.1 and 200.0.0.1 are some examples of IP address in dotted-decimal notation.

Subnet Mask

Subnet mask is used to separate the network address from the host address in IP address. As we discussed earlier an IP address is the combination of network address and host address, subnet mask helps us and programs which use IP address in identifying the network portion and the host portion.

Just like IP address, subnet mask is also 32 bits in length and uses same notations which IP address uses to present itself.

Subnet mask assigns an individual bit for each bit of IP address. If IP bit belongs to network portion, assigned subnet mask bit will be turned on. If IP bit belongs to host portion, assigned subnet mask bit will be turned off.

In binary notation, 1 (one) represents a turned on bit while 0 (zero) represents a turned off bit. In dotted-decimal notation, a value range 1 to 255 represents a turned on bit while a value 0 (zero) represents a turned off bit.

An IP address is always used with subnet mask. Without subnet mask, an IP address is an ambiguous address in IP network.

ip address classes

IP address classes



There are 4,294,967,296 IP addresses. Managing all these addresses without any scheme are next to impossible. Let’s understand it with a simple example. If you have to find out a word from a language dictionary, how long will you take? Usually you will take less than five minutes to find out that word. You are able to do this because words in dictionary are organized in alphabetic order. If you have to find out the same word from the dictionary which does not use any sequence or order to organize the words, how long will you take this time? It may take up to one week to find out that specific word from all words. If an unorganized dictionary which roughly contains 1 billion words can turn a five minutes task in a one week task than suppose how nearly 4.3 billion addresses will make a search task complicated if they are unorganized.

For easier management, IP addresses are organized in numeric order and divided in following five classes.

Class Starting Address Ending Address Subnet mask
A 0.0.0.0 127.255.255.255 255.0.0.0
B 128.0.0.0 191.255.255.255 255.255.0.0
C 192.0.0.0 223.255.255.255 255.255.255.0
D 224.0.0.0 239.255.255.255 255.255.255.255
E 240.0.0.0 255.255.255.255 255.255.255.255

As we discussed earlier, an IP address is the combination of network address and host address. In each IP address, few bits are reserved for network address. In class A, B and C first 8, 16 and 24 bits are reserved respectively for network addresses.

ip address classes

How to find the class of an IP address?

To find the class of an IP address, simply pay attention on the first octet.

If the value of first octet is in range 1 to 127, it’s a class A IP address. Examples of class A IP address are: – 1.2.3.4, 10.20.30.45, 125.234.123.23, 126.100.200.45, etc.

If the value of first octet is in range 128 to 191, it’s a class B IP address. Examples of class B IP address are: – 128.200.100.50, 191.200.100.1, 172.168.0.1, 175.45.48.14, etc.

If the value of first octet is in range 192 to 223, it’s a class C IP address. Examples of class C IP address are: – 192.168.1.1, 200.0.0.1, 223.224.127.1, 212.14.15.56, etc.

Private IP address and Public IP address

Based on accessibility, IP addresses are mainly divided in two categories; private IP addresses and public IP addresses. Differences between private IP addresses and public IP addresses are following.

Private IP addresses

Private IP addresses are the IP addresses which are reserved for local networks and cannot be accessed from a public network such as Internet. Vice versa a public network cannot be accessed from a private IP address.

Following IP ranges are reserved for private IP addresses.

  • 10.0.0.0 to 10.255.255.255
  • 172.16.0.0 to 172.31.255.255
  • 192.168.0.0 to 192.168.255.255

Public IP addresses

Public IP addresses are the IP addresses which are publicly accessible from any public network such as Internet. In order to access a public IP address, we must have to use a public IP address.

Except private IP addresses, all IP addresses of class A, B and C are public IP addresses.

Special IP addresses

Special IP addresses are the IP addresses which are reserved for network testing and troubleshooting. These IP addresses cannot be assigned to an end device or an interface. Following addresses are reserved for special purpose: –

0.0.0.0:- This is the first IP address of IP addresses. It represents all networks.

127.0.0.0 to 127.255.255.255: – Reserved for IP protocol testing and troubleshooting. Virtual interfaces such as loopback adaptor use this IP range for addressing.

224.0.0.0 to 239.255.255.255 (Class D): – Reserved for multicast addresses. A multicast address is an address which has multiple recipients.

240.0.0.0 to 255.255.255.255 (Class E): – Reserved for future use. These addresses are not used currently for any purpose.

255.255.255.255:- This is the last IP address of IP addresses. It represents all hosts.

That’s all for this tutorial. If you have any comment, suggestion or feedback about this tutorial, please mail me. If you like this tutorial, please don’t forget to share it with your friends through your favorite social platform.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

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Networking Tutorials

Full Form of Hardware and Networking Devices

Searching for full form of any computer related term or looking for what a term stands for in computer world, here is the A to Z list of most common computer hardware and networking terms in abbreviated form as well as in full form with description.

Full Form of Hardware and Networking Devices

Abbreviated Form Full Form Description
AC alternating current
ACPI advanced configuration and power interface
ACT activity
ADSL asymmetrical digital subscriber line
ADSP AppleTalk data stream protocol
AEP AppleTalk echo protocol
AFP AppleTalk Filing protocol
AGP accelerated graphics port
AMD advanced micro devices
AMR audio modem riser
APIPA automatic private internet protocol addressing
API Application Programming Interface
APPC Advanced Peer to Peer Communications
APPN Advanced Peer to Peer Networking
APM advanced power management
ARP address resolution protocol
ASR automated system recovery
ARCnet Attached Resource Computer Network
ARP Address resolution Protocol
ARUP AppleTalk update routing Protocol
ASP AppleTalk session protocol
AT advanced technology
ATA advanced technology attachment
ATAPI advanced technology attachment packet interface
ATM asynchronous transfer mode
ATX advanced technology extended
ATP AppleTalk Transaction Protocol
AU Access Unit
AUI Attachment unit interface


BDC Backup Domain Controller
BIOS basic input/output system
BGP Border Gateway Protocol
BNC Bayonet-Neill-Concelman or British Navel Connector
BOOTP Boot Protocol
BRI basic rate interface
BSC Binary Synchronous Communication
BTX balanced technology extended
CCD charged coupled device
CD compact disc
CD-ROM compact disc-read-only memory
CD-RW compact disc-rewritable
CDFS compact disc file system
CHAP Challenge Handshake Authentication Protocol
CIDR Classless Inter Domain Routing
CMOS complementary metal-oxide semiconductor
CNR communication network riser
COM1 communication port 1
CPU central processing unit
CRIMM continuity-rambus inline memory module
CRT cathode-ray tube
CSU Channel service unit
DAC discretionary access control
DAS Dual attachment stations
DAT Digital Audio Tape
DB-25 serial communications D-shell connector, 25 pins
DB-9 9 pin D shell connector
DBMS Database Management Systems
DC direct current
DCE Data communications equipment
DDOS distributed denial of service
DDR double data-rate
DDR RAM double data-rate random access memory
DDR SDRAM double data-rate synchronous dynamic random access memory
DDP Datagram Delivery Protocol
DDS Digital data service
DFS distributed file system
DHCP dynamic host configuration protocol
DIMM dual inline memory module


DLC Data Link Control
DIN Deutsche Industrie Norm
DIP dual inline package
DLT digital linear tape
DLP digital light processing
DMA direct memory access
DNA Digital Network Architecture
DNS domain name service or domain name server
DOS disk operating system or denial of service
DPMS display power management signaling
DRAM dynamic random access memory
DRDA Distributed Relational Database Architecture
DSL digital subscriber line
DVD digital video disc or digital versatile disc
DVD-RAM digital video disc-random access memory
DVD-ROM digital video disc-read only memory
DVD-R digital video disc-recordable
DVD-RW digital video disc-rewritable
DSU Digital service unit
DTD Document Type Definition
DTE Data terminal equipment
DUN Dial up networking
DVM Digital volt meter
DVI digital visual interface
ECC error correction code
ECP extended capabilities port
EEPROM electrically erasable programmable read-only memory
EFS encrypting file system
EGP Exterior Gateway Protocol
EIDE enhanced integrated drive electronics
EISA extended industry standard architecture
EIA Electronic Industries Association
EMI electromagnetic interference
EMP electromagnetic pulse
EPROM erasable programmable read-only memory
EPP enhanced parallel port
ERD emergency repair disk
ESD electrostatic discharge
ESDI enhanced small device interface
EVGA extended video graphics adapter/array
EVDO evolution data optimized or evolution data only
FAT file allocation table
FAT12 12-bit file allocation table
FAT16 16-bit file allocation table
FAT32 32-bit file allocation table
FDD floppy disk drive
FDDI Fiber Distributed Data Interface
FERPA Family Educational Rights and Privacy Act
Fn Function (referring to the function key on a laptop)
FPM fast page-mode
FRU field replaceable unit
FT P file transfer protocol
FTP File Transport Protocol
FQDN fully qualified domain name
GB gigabyte
GDI graphics device interface
GHz gigahertz
GUI graphical user interface
GPRS general packet radio system
GSM global system for mobile communications
HAL hardware abstraction layer
HCL hardware compatibility list
HDD hard disk drive
HDMi high definition media interface
HPFS high performance file system
HTML hypertext markup language
HTTP hypertext transfer protocol
HTTPS hypertext transfer protocol over secure sockets layer
I/O input/output
IAB Internet Architecture Board
IANA Internet Assigned Numbers Authority
ICMP internet control message protocol
ICS internet connection sharing
ICR intelligent character recognition
IDE integrated drive electronics
IEEE Institute of Electrical and Electronics Engineers
IETF Internet Engineering Task Force
IGMP Internet Group Management Protocol
IIS Internet Information Services
IMAP internet mail access protocol
IMAP4 Internet Mail Access Protocol version 4
IP internet protocol
IPCONFIG internet protocol configuration
IPP internet printing protocol
IPSEC internet protocol security
IPX internetwork packet exchange
IPX/SPX internetwork packet exchange/sequenced packet exchange
IR infrared
IrDA Infrared Data Association
IRQ interrupt request
IRTF Internet Research Task force
ISA Industry Standard Architecture
ISAKMP Internet Security Association and Key Management Protocol Authentication
ISDN Integrated Services Digital Network
ISP Internet Service Provider
ISOC Internet Society, promotes internet policies
ISA industry standard architecture
ISDN integrated services digital network
ISO Industry Standards Organization
ISP internet service provider
ITU International Telecommunication Union
KB kilobyte
L2F Layer2 Forwarding
L2TP Layer 2 tunneling protocol
LAN local area network
LBA logical block addressing
LC Lucent connector
LCD liquid crystal display
LDAP lightweight directory access protocol
LDA Local delivery agent
LED light emitting diode
LIP or LiPoly lithium-ion polymer
Li-on lithium-ion
LPD/LPR line printer daemon / line printer remote
LPT line printer terminal
LPT1 line printer terminal 1
LPX low profile extended
LU Logical Units
LVD low voltage differential
MAC media access control
MAN metropolitan area network
MAPI messaging application programming interface
Mb megabit
MB megabyte
MBR master boot record
MBSA Microsoft Baseline Security Analyzer
MCI Micro-channel architecture
MCR multivariant curve resolution
MFD multi-function device
MFP multi-function product
MHz megahertz
MicroDIMM micro dual inline memory module
MIB Management Information BASE
MIDI musical instrument digital interface
MIME multipurpose internet mail extension
MLI multiple link interface
MMC Microsoft management console
MSSP managed security service provider
MSTP Multiple Spanning Tree Protocol
MMX multimedia extensions
MOTIS Message oriented text interchange system
MP3 Moving Picture Experts Group Layer 3 Audio
MPEG Moving Picture Experts Group
MS Message Store
MSCONFIG Microsoft configuration
MSDS material safety data sheet
MUI multilingual user interface
MTA Message transfer agent
MTU Maximum Transmission Unit
NADN Nearest Active Downstream Neighbor
NAS network-attached storage, network access server
NAU Network Addressable Units
NAUN Nearest Active Upstream Neighbor
NAT network address translation
NBF NetBIOS Frame Protocol
NBNS NetBIOS Name Server
NBP Name binding protocol
NBT NetBIOS over TCP/IP
NCP NetWare Core Protocol
NCP Network Control Program
NDIS Network Driver Interface Specification
NFS Network File System
NetBIOS networked basic input/output system
NetBEUI networked basic input/output system extended user interface
NFS network file system
NIC network interface card
NiCd nickel cadmium
NiMH nickel metal hydride
NLI not logged in or natural language interface
NLX new low-profile extended
NNTP network news transfer protocol
NOS Network Operating System
NTFS new technology file system
NTLDR new technology loader
NWLINK Netware Link
OC Optical Carrier
OCR optical character recognition
ODBC Open Database Connectivity
ODI Open Data link Interface
OSI Open Systems Interconnect
OEM original equipment manufacturer
OMR optical mark recognition
OS operating system
OSR original equipment manufacturer service release
OSPF Open Shortest Path First
PAP Password Authentication Protocol
PAP Printer access protocol
PAN personal area network
PATA parallel advanced technology attachment
PC personal computer
PCI peripheral component interconnect
PCIe peripheral component interconnect express
PCIX peripheral component interconnect extended
PCL printer control language
PCMCIA Personal Computer Memory Card International Association
PDA personal digital assistant
PDC Primary Domain Controller
PDL Page description language
PDN Public data network
PGA pin grid array
PGA2 pin grid array 2
PIN personal identification number
PKI public key infrastructure
PnP plug and play
POP post office protocol
POP3 post office protocol 3
POST power-on self test
POTS plain old telephone service
PPP point-to-point protocol
PPTP point-to-point tunneling protocol
PRI primary rate interface
PROM programmable read-only memory
PS/2 Personal System/2 connector
PSTN public switched telephone network
PU Physical Units
PVC permanent virtual circuit
PXE preboot execution environment
QoS quality of service
RADIUS Remote Authentication Dial In User Service
RAID redundant array of independent (or inexpensive) discs
RAM random access memory
RARP Reverse Address Resolution Protocol
RAS remote access service
RBAC role-based access control or rule-based access control
RDRAM RAMBUS dynamic random access memory
RF radio frequency
RFI radio frequency interference
RGB red green blue
RIMM RAMBUS inline memory module
RIP routing information protocol
RIS remote installation service
RISC reduced instruction set computer
RJ registered jack
RJ-11 registered jack function 11
RJ-45 registered jack function 45
RMA returned materials authorization
ROM read only memory
RPC Remote Procedure Call
RR Resource Records
RS-232 or RS-232C recommended standard 232
RTC real-time clock
RTMP Routing table maintenance protocol
SAN storage area network
SAP Service Advertising Protocol
SAS Single Attachment stations
SATA serial advanced technology attachment
SC subscription channel
SCSI small computer system interface
SCSI ID small computer system interface identifier
SD card secure digital card
SDRAM synchronous dynamic random access memory
SDH Synchronous Digital Hierarchy
SDLS Synchronous Data Link Control
SEC single edge connector
SFC system file checker
SGRAM synchronous graphics random access memory
SGML Standardized General Markup Language
SIMM single inline memory module
SLI scalable link interface or system level integration or scanline interleave mode
SLED Single Large Inexpensive disk
SLIP Serial Line interface Protocol
SMAU Smart Multi station Access Unit
SMB server message block or small to midsize business
SMDS Switched Multimegabit Data Service
SMS Systems Management Server
SMTP simple mail transport protocol
SNA System Network Architecture
SNMP simple network management protocol
SoDIMM small outline dual inline memory module
SOHO small office/home office
SONET Synchronous Optical Network
SP service pack
SP1 service pack 1
SP2 service pack 2
SPDIF Sony-Philips digital interface format
SPGA staggered pin grid array
SPX sequenced package exchange
SRAM static random access memory
SSH secure shell
SSID service set identifier
SSL secure sockets layer
SQL Structured Query Language
SSCP Systems Services Control
ST straight tip
STP shielded twisted pair
SVGA super video graphics array
SVC Switched virtual circuit
SXGA super extended graphics array
TB terabyte
TCP transmission control protocol
TCP/IP transmission control protocol/internet protocol
TDI Transport Driver Interface
TDR time domain reflectometer
TFTP trivial file transfer protocol
TIA Telecommunications Industries Association
TLD Top Level domain
UA Users agent
UART universal asynchronous receiver transmitter
UDF user defined functions or universal disk format or universal data format
UDMA ultra direct memory access
UDP user datagram protocol
UL Underwriter’s Laboratory
UNC universal naming convention
UPS uninterruptible power supply
URL uniform resource locator
USB universal serial bus
USMT user state migration tool
UTP unshielded twisted pair
UXGA ultra extended graphics array
VESA Video Electronics Standards Association
VFAT virtual file allocation table
VGA video graphics array
VoIP voice over internet protocol
VIM Vendor Independent Messaging protocol
VPN virtual private network
VRAM video random access memory
VPN Virtual Private Networking
W3C World Wide Web Consortium
WAN wide area network
WAP wireless application protocol
WEP wired equivalent privacy
WIFI wireless fidelity
WINS windows internet name service
WLAN wireless local area network
WPA wireless protected access
WUXGA wide ultra extended graphics array
XGA extended graphics array
XML Extensible Markup Language
ZIF zero-insertion-force
ZIP zigzag inline package

That’s all for this tutorial. We frequently add new abbreviated form with description in this list. Keep visiting this page for the current list.
If you like this tutorial, please share it with your friends.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

Categories
Networking Tutorials

Computer Networking Devices Explained with Function

This tutorial explains the functions of the most common and the essential networking devices (such as Hub, Switch, Router, Bridge, Modem, NIC, Proxy and Gateway) in detail with examples.

Network Interface Card (NIC)

In the list of the networking devices, NIC stands on the first place. Without this device, networking cannot be done. This is also known as network adapter card, Ethernet Card and LAN card. NIC allows a networking device to communicate with the other networking device.

NIC converts the data packets between two different data transmission technologies. A PC uses parallel data transmission technology to transmit the data between its internal parts while the media that provides connectivity between different PCs uses serial data transmission technology.



A NIC converts parallel data stream into the serial data stream and the serial data stream into the parallel data stream.

nic functions

Typically all modern PCs have the integrated NICs in the motherboards. If additional NICs are required, they are also available as add-on devices separately.

For desktop or server system, they are available in the adapter form which can be plugged into the available slots of the motherboard. For laptop or other small size devices, they are available in the PCMCIA (Personal Computer Memory Card International Association) card form which can be inserted into the PCMCIA slot.

Types of NICs

There are two types of NICs.

Media Specific: – LAN card are used according to the media type. Different types of the NICs are used to connect the different types of media. To connect a specific media type, we must have to use a NIC which is particularly made for that type of media.

Network Design Specific: – A specific network design needs a specific LAN card. For example FDDI, Token Ring and Ethernet have their own distinctive type of NIC cards. They cannot use other types of NIC cards.

Following figure illustrates some common types of NICs.

types of nics

Hub

Hub is a centralized device that connects multiple devices in a single LAN network. When Hub receives the data signals from a connected device on any of its port, except that port, it forwards those signals to all other connected devices from the remaining ports. Usually, Hub has one or more uplink ports that are used to connect it with another Hub.

There are two types of the Hub.

Passive Hub: – It forwards data signals in the same format in which it receives them. It does not change the data signal in any manner.

Active Hub: – It also works same as the passive Hub works. But before forwarding the data signals, it amplifies them. Due to this added feature, the active Hub is also known as the repeater.

networking device hub

Hubs are no longer used in the computer networks.

MAU and Patch panel

MAU and Patch Panel look like the Hub, but they are different. MAU (Multi Access Unit) is the sibling of Hub for the token ring network. Differences between Hub and MAU are the following: –

  • Hub is used for the Ethernet Network while the MAU is used for the Token ring network.
  • Hub creates logically star topology while MAU creates logically ring topology.

mau

Patch panel is used to organize the UTP cables systematically. It doesn\’t interfere in the data signals.

patch panel

Bridge

Bridge is used to divide a large network into smaller segments. Basic functions of the Bridge are the following: –

  • Breaking a large network into smaller segments.
  • Connecting different media types. Such as connects UTP with the fiber optic.
  • Connecting different network architectures. Such as connects Ethernet with the Token ring.

functions of bridge

A Bridge can connect two different types of media or network architecture, but it cannot connect two different types of network layer protocol such as TCP/IP or IPX. Bridge requires the same network layer protocol in all segments.

There are three types of Bridge:-

Local Bridge: – This Bridge connects two LAN segments directly. In Ethernet Implementation, it is known as the Transparent Bridge. In Token Ring network, it is called the Source-Routed Bridge.

local bridge

Remote Bridge: – This Bridge connects with another Bridge over the WAN link.

remote bridge

Wireless Bridge: – This Bridge connects with another Bridge without using wires. It uses radio signals for the connectivity.

wireless bridge

In OSI Layers /TCP-IP networking models, the functionalities of the Bridges are defined in the physical layer and data link layer.

Just like Hubs, Bridge no longer used in the computer network. Bridges have been replaced by the Switches.

Switch



Just like Hub and Bridge, Switch is also used to connect the multiple devices together in a LAN segment. Basically, a Switch is the upgraded version of the Bridge. Besides providing all the functionalities of Bridge, it also offers several additional features.

The biggest advantage of Switch is that, it makes switching decisions in hardware by using application specific integrated circuits (ASICs).

Unlike the generic processors that we use in our PC, ASICs are the specialized processors built only to perform very few particular tasks. Usually, the ASICs in the Switches have single task and that is the switching the frames as fast as possible.

An ASIC occupied switch performs this task blazingly fast. For example, an entry level Catalyst Switch 2960 can process 2.7 million frames per second.

switch

Modem

In simple language, a Modem is the device that is used to connect with the Internet. Technically, it is the device that enables the digital data to be transmitted over the telecommunication lines.

A Telco company uses entirely different data transmission technology from the technology that a PC uses for the data transmission. A modem understands both technologies. It changes the technology that a PC uses, in the technology which Telco Company understands.

It enables communication between the PC (Known as the DTE device) and the Telecom company\’ office (Known as the DCE device).

functions of modem

Following figure shows some common types of the Modem.

types of modem

Gateway

Gateway is used to forward the packets which are generated from the local host or network and but intended for the remote network. If a data packet does not find its destination address in the local network then it takes the help of the gateway device to find the destination address in the remote network. A gateway device knows the path of the remote destination address. If require, it also changes the encapsulation of the packet so it can travel through the other networks to get its destination address.

gateway

Examples of the Gateway

Email Gateway: – Translates SMTP e-mail in standard X.400 format before forwarding.

GSNW Gateway: – Allows Windows clients to access resources from the NetWare server.

PAD Gateway: – Provides connectivity between LAN network and X.25 network.

Router

The router connects the different network segments. It switches the data packets between those networks which are either located in the different logical segments or built with the different network layer protocols.

When a router receives a data packet on any of its interface, it checks the destination address of that packet and based on that destination address, it forwards that data packet from the interface which is connected with the destination address.

To forward a data packet to its destination, router keeps the records of connected networks. These records are maintained in a database table known as the routing table. Routing table can be built statically or dynamically.

router

Basically routers are used: –

  • To connect different network segments.
  • To connect different network protocols such as IP and IPX.
  • To connect several smaller networks into a large network (known as the Internetwork)
  • To break a large network into smaller networks (Known as the Subnets. Usually created to improve the performance or manageability.)
  • To connect two different media types such as UTP and Fiber optical.
  • To connect two different network architectures such as Token Ring and Ethernet.
  • To connect LAN network with Telco company’ office (Known as the DTE device).
  • To access DSL services (known as the DSL Router).

Proxy

Proxy is used to hide the internal network from external world. It can be a dedicate device or can be an application software. Once it is configured, all communication goes through it. Since external devices cannot access the internal devices directly, they cannot tamper with the internal devices.

proxy

Transceiver

Transceiver is a small device that has the capability of receiving and sending both types of signals; analog and digital. Usually, it is inbuilt in network interface card. But, it is also available as an individual device. It detects the type of signal from the network wire and converts the passing signal accordingly.

For example, a transceiver is attached with a device that transmits signal in digital form. Now suppose, this device is connected with the network wire that uses analog form for data transmission. In this case, transceiver converts digital signals in the analog signals before placing them in the network wire.

transceiver

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

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Networking Tutorials

What is Networking Explained with Examples

This tutorial explains the definition, purpose and benefits of the computer networking in detail. Learn what the computer networking is and what the advantages of computer networking are in easy language with examples.

What is the Computer Networking?

Computer networking is the subject which explains how computers connect with each other for sharing resource and information and what technologies and devices they use for the connectivity.

Benefits of Networking

Computer networking provides the following benefits.

  • It allows us to share data and resources.
  • It helps us in reducing the required number of devices.
  • It provides us a platform to communicate with other users in network.
  • It allows multiple users to work on a single project.
  • It allows us to store data in a centralize location.
  • It allows us to implement the security policies.
  • It allows us to track and monitor the use of resources.

Purpose of Computer Networking



The main purpose of computer networking is the sharing. It allows us to share mainly three things; data, resources, and applications. Let’s understand each of these in detail.

Data sharing

Networking allows us to share data between connected devices. Let’s take a simple example. Suppose there are two computers which exchange data on regular basis. Without networking, the following steps are required to exchange data between them.

  • In sender PC, write data in an external device (such as CD, DVD and USB)
  • Move that external device to the receiver PC
  • In receiver PC, read or copy the data from that external device

If the data is exchanged 100 times a day, we have to follow these steps 100 times a day. In such a situation, where the data is often exchanged, this method is neither convenient nor appropriate.

computers without networking

In this case, networking is a better solution. Once networking is done, we can exchange any amount of data between connected devices at any time without using any external device.

computers with networking

Resources Sharing

Networking allows us to share devices among the computers. By sharing the devices, we can reduce the number of required components in the network.
Let\’s understand this with a simple example.

Four computers are used in a small office. Computers are not connected with others. Each computer generates some print jobs daily.

To fulfill the print requirement of each computer, without networking, we have to buy the four printers; one for each.

sharing resources in network

By connecting these computers through networking, we can reduce the required number of printers up to one. Once networking is done, only one printer will be sufficient to meet the print requirement of all computers.

sharing printer in network

When we reduce the number of essential devices, the cost of the network is also reduced.
In the preceding example, without networking, we require four printers, whereas with networking we only require one printer. Thus, through the networking we can save the cost of three printers.

There are two types of device: –

Shareable: – Devices which can be shared in the network such as hard disk, printer, modem, scanner, CD, DVD, USB etc.

Non-Shareable: – Devices which cannot be shared in the network such as CPU, RAM, Motherboard, Monitor, etc.

Although advance networking techniques, such as cloud computing, allow the sharing of any resource including the CPU and the RAM, but for the initial level, you should stick with the traditional types listed above; shareable and non-shareable. This will help in understanding the complex networking concepts in a simple way.

Application Sharing



Just like data and resource, through the networking we can also share an application. In Application sharing, an application is installed in two parts; server application and client application. Both parts are used to provide and request service or data respectively.

Let\’s take a simple example.

A user connects his system to the Internet and watches a video on YouTube. YouTube, which provides the requested video, is the example of a server application. And the browser or app, that the user uses to watch the video, is the example of a client application.

application sharing

Application sharing is mostly used in company environment. In companies, usually a project is assigned to several users or a team which have several members. Networking allows concerned users or members to work on assigned project simultaneously. Besides this, it is also used for the troubleshooting and accessing a networking device or a computer remotely.

Networking not necessary always

Networking is complex process. Adding devices in a network requires special networking devices such as cables, switches, routers, etc. In addition, to add a computer to the network, we also have to adjust or change its configuration settings.

Networking should be done only when it is really required. For example, for the data sharing it should be done only when the data that needs to be shared is in the large amount or it is often exchanged. For example if you only need to share a single file between two PCs, setting up networking in this situation is a completely worthless idea.

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo

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Networking Tutorials

Networking Basic Concepts and Fundamentals Explained

This tutorial explains the basic and fundamental concepts of the computer networking. Learn the essential networking topics in detail with examples.

Computer networking is one of the most complex subjects. Describing all of its topics requires an encyclopedia. Learning and understanding all these topics at the primary stage are neither required nor recommended. It is just like learning the vocabulary from the dictionary. Unless you know what you need to know, you would not learn what you should learn.

I have already explained the definition, purpose and benefits of the computer networking in the following article.

What is computer networking explained with examples

In this tutorial, I will discuss two essential topics that you should learn at the elementary level. Understanding these topics will set the foundation for the rest of your studies.

Essential components of the computer network

When learning computer networking, this should be your first topic. A computer is built from the four essential components; End devices, Media, Protocols and Networking devices. Let’s understand each of these components.

End devices



An end device is the device that sends or receives the data or service in the network. An end device might be a PC, Laptop, Smartphone or any other device that is capable of the sending and receiving data the data and connected with the network. To build a network, at least two end devices are required.

end devices

Broadly end devices are categorized in two types; server end device and client end device. Server end device is the device which provides data or service. Client end device is the device which receives the offered data or service from the server end device.

Media

The media provides connectivity between the end devices. Unless end devices are connected through the any kind of media, they cannot exchange the data or service. Mainly there are two types of media; Wireless media and wired media.

In wireless media, radio signals are used to transfer the data between end devices, whereas in wired media, the data is transferred through cables.

Both media types are further classified into several subtypes. Subtypes are categorized based on the various factors such as length, data transfer speed, used metal, frequency band, etc. Subtypes are defined as the media standards. Two common media standards are the Ethernet and the IEEE802.11 or Wi-Fi standards.

media types

The Ethernet defines the standards for the wired media. The IEEE802.11 or Wi-Fi defines the standards for the wireless media.

Protocols



Protocols enable communication between two or more end devices. A protocol is a set of predefined rules that specifies standards for a particular stage or all stages of the communication.

Following are the some common functions performed by the protocols.

  • Initializing and terminating the communication process
  • Performing encryption and compression before sending the data
  • Packing data in such a format that it can travel in the network
  • Providing logical addressing
  • Performing error correction
  • Performing authentication

http protocol example

Two popular networking models; OSI Reference model and TCP/IP model describe the functionalities of the most common protocols. Both models divide the entire communication process in logical layers. Further, they explain how the protocols work in each layer to enable the communication process.

Networking device

A networking device works between the end devices. It controls and forwards the flow of data. Based on the functionalities, a networking device can be categorized in three types; forwarding device, connecting device and the securing device.

networking devices

A forwarding device forwards the data. This device usually has multiple ports which are used to connect more than two end devices in a single network. Hub, bridge and Ethernet switch provide this functionality.

A connecting device connects two or more different types of media and protocols. If two end devices are located in the different logical networks or connected through the different types of media, they need a connecting device to exchange the data. Router and Multilayer switch provide this functionality.

A securing device secures the data from unauthorized access. When data packet arrives to it, based on pre-defined rules it performs security checks and takes the forwarding decision. Common devices which provide this functionality are the Firewall and NAT.

Classification of the computer network

Once you learned the essential components of the network, this should be your next topic. Computer networks are mainly categorized based on the geographical location, access types and relationship between end devices.

Based on the geographical location

Based on the geographical coverage, the network is classified into three types; LAN, MAN and WAN. Network that is geographically spread over a small, medium and large area is known as the LAN, MAN and WAN network respectively.

Based on the access type

On the basis of allowing users to access network resources, the network is classified into three types; Intranet, Extranet and Internet. An Intranet is a private network. In this network, external users are not allowed to access the network resources. An Extranet is also a private network. But in this network, after proper authorization, external users are allowed to access a small portion of the network. The Internet is the public network. Any user can connect with this network.

Based on the relationship between the end devices

Based on how the end devices access each other, the network is categorized in two types; peer to peer network and clients/server network. In peer to peer network, all end devices have equal rights. In clients/server network, server decides which client will have what rights.

Resources for further study

To learn the foundation topics introduced above, you can use the following tutorials.

OSI Seven Layers Model Explained with Examples

This tutorial explains the seven layers of OSI Reference model.

TCP/IP Reference Model Explained

This tutorial explains five layers of TCP/IP model (Application, Transport, Internet or Network, Data Link and Physical) and their functionality in detail.

Types of Computer Network Explained in Easy Language

This tutorial explains the different types of computer network and their characteristics in easy language.

Computer Networking Devices Explained with Function

This tutorial explains the functions of the most common and the essential networking devices in detail with examples.

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it through your favorite social network.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

Full Version 200-301 Dumps

Try 200-301 Dumps Demo