Slive: 2011

Saturday, December 10, 2011

Feature of Windows 7

Windows 7

You can learn from this video that how to take screen shots in a sequence to record them

one by one to solve any Problem occurring in your PC.

For more video's

Visit

My YouTube Channel

http://www.youtube.com/user/mrroles17

Follow @sukhi_11

Saturday, June 18, 2011

Different versions of Windows 7

Microsoft provides 6 versions of Window 7.Different versions having different features.

Starter is only used in USA, on small notebook PC's.

Home Basic only in emerging markets(e.g. Brazil,thailland).

Home Premium is aimed at the home user market.

Professional is the first edition aimed at the business market.

Enterprise & Ultimate Editions both are same in all the features only difference in the license.It contains all the features.

Click on the image to view.

Tuesday, March 15, 2011

Internet Protocol version 6 (IPv6) is a version of the Internet Protocol (IP) that is designed to succeed Internet Protocol version 4 (IPv4). The Internet operates by transferring data in small packets that are independently routed across networks as specified by an international communications protocol known as the Internet Protocol. Each data packet contains two numeric addresses that are the packet's origin and destination devices. Since 1981, IPv4 has been the publicly used version of the Internet Protocol, and it is currently the foundation for mostInternet communications. The Internet's growth has created a need for more addresses than IPv4 is capable of. IPv6 allows for vastly more numerical addresses, but switching from IPv4 to IPv6 may be a difficult process.

An ipv6 address is represented by eight blocks of four hexadecimals digits separted by colon. Each block of ipv6 address represents a 16-bit number.The following is the example of ipv6 address.

2001:0db8:3c4d:0015:0000:0000:abcd:ef12

The preceding address can also be represented after eliminating the leading zeroes in the address:

2001:db8:3c4d:15:0:0:abcd:ef12

The preceding address can also be shortened further by replacing all adjacent zeros blocks by a single set of double colons(only once in the IP address), as follows:

2001:db8:3c4d:15::abcd:ef12

For the Detail of IPv6 Click on the image below:

Types of Ipv6 Addresses:-

(1)-LINK LOCAL

ü Self-Generated

ü Only works in LAN(Local Area Network)

ü FE80::/10

(2)-UNIQUE LOCAL

ü Private IP

ü Fc00::/7

(3)-GLOBAL IP

ü Public IP

ü 2001::/3

Monday, February 14, 2011

Cisco Router Configuration

1. What this document covers

There are several methods available for configuring Cisco routers. It can be done over the network from a TFTP server. It can be done through the menu interface provided at bootup, and it can be done from the menu interface provided by using the command setup. This tutorial does not cover these methods. It covers configuration from the IOS command-line interface only.
Note that this tutorial does not cover physically connecting the router to the networks it will be routing for. It covers operating system configuration only.

1.1 Reasons for using the command-line

The main reason for using the command-line interface instead of a menu driven interface is speed. Once you have invested the time to learn the command-line commands, you can perform many operations much more quickly than by using a menu. This is basically true of all command-line vs. menu interfaces. What makes it especially efficient to learn the command-line interface of the Cisco IOS is that it is standard across all Cisco routers.

2. Getting started with Cisco

Initially you will probably configure your router from a terminal. If the router is already configured and at least one port is configured with an IP address, and it has a physical connection to the network, you might be able to telnet to the router and configure it across the network. If it is not already configured, then you will have to directly connect to it with a terminal and a serial cable. With any Windows box you can use Hyperterminal to easily connect to the router. Plug a serial cable into a serial (COM) port on the PC and the other end into the console port on the Cisco router. Start Hyperterminal, tell it which COM port to use and click OK. Set the speed of the connection to 9600 baud and click OK. If the router is not on, turn it on.
If you wish to configure the router from a Linux box, either Seyon or Minicom should work. At least one of them, and maybe both, will come with your Linux distribution.
Often you will need to hit the Enter key to see the prompt from the router. If it is unconfigured it will look like this:

Router>

If it has been previously configured with a hostname, it will look like this:

hostname of router>

If you have just turned on the router, after it boots it will ask you if you wish to begin initial configuration. Say no. If you say yes, it will put you in the menu interface. Say no.

2.1 Modes

The Cisco IOS command-line interface is organized around the idea of modes. You move in and out of several different modes while configuring a router, and which mode you are in determines what commands you can use. Each mode has a set of commands available in that mode, and some of these commands are only available in that mode. In any mode, typing a question mark will display a list of the commands available in that mode.

Router>?

2.2 Unprivileged and privileged modes

When you first connect to the router and provide the password (if necessary), you enter EXEC mode, the first mode in which you can issue commands from the command-line. From here you can use such unprivileged commands as ping, telnet, and rlogin. You can also use some of the show commands to obtain information about the system. In unprivileged mode you use commands like, show version to display the version of the IOS the router is running. Typing show ? will diplay all the show commands available in the mode you are presently in.

Router>show ?

You must enter privileged mode to configure the router. You do this by using the command enable. Privileged mode will usually be password protected unless the router is unconfigured. You have the option of not password protecting privileged mode, but it is HIGHLY recommended that you do. When you issue the command enable and provide the password, you will enter privileged mode.
To help the user keep track of what mode they are in, the command-line prompt changes each time you enter a different mode. When you switch from unprivileged mode to privileged mode, the prompt changes from:

Router>

Router#

This would probably not be a big deal if there were just two modes. There are, in fact, numerous modes, and this feature is probably indispensable. Pay close attention to the prompt at all times.
Within privileged mode there are many sub-modes. In this document I do not closely follow Cisco terminology for this hierarchy of modes. I think that my explanation is clearer, frankly. Cisco describes two modes, unprivileged and privileged, and then a hierarchy of commands used in privileged mode. I reason that it is much clearer to understand if you just consider there to be many sub-modes of privileged mode, which I will also call parent mode. Once you enter privileged mode (parent mode) the prompt ends with a pound sign (#). There are numerous modes you can enter only after entering privileged mode. Each of these modes has a prompt of the form:

Router(arguments)#

They still all end with the pound sign. They are subsumed within privileged mode. Many of these modes have sub-modes of their own. Once you enter priliged mode, you have access to all the configuration information and options the IOS provides, either directly from the parent mode, or from one of its submodes.

3. Configuring your Cisco Router

If you have just turned on the router, it will be completely unconfigured. If it is already configured, you may want to view its current configuration. Even if it has not been previously configured, you should familiarize yourself with the show commands before beginning to configure the router. Enter privileged mode by issuing the command enable, then issue several show commands to see what they display. Remember, the command show ? will display all the showcommands aavailable in the current mode. Definately try out the following commands:

Router#show interfaces
Router#show ip protocols
Router#show ip route
Router#show ip arp

When you enter privileged mode by using the command enable, you are in the top-level mode of privileged mode, also known in this document as "parent mode." It is in this top-level or parent mode that you can display most of the information about the router. As you now know, you do this with the show commands. Here you can learn the configuration of interfaces and whether they are up or down. You can display what IP protocols are in use, such as dynamic routing protocols. You can view the route and ARP tables, and these are just a few of the more important options.
As you configure the router, you will enter various sub-modes to set options, then return to the parent mode to display the results of your commands. You also return to the parent mode to enter other sub-modes. To return to the parent mode, you hit ctrl-z. This puts any commands you have just issued into affect, and returns you to parent mode.

3.1 Global configuration (config)

To configure any feature of the router, you must enter configuration mode. This is the first sub-mode of the parent mode. In the parent mode, you issue the command config.

Router#config
Router(config)#

As demonstrated above, the prompt changes to indicate the mode that you are now in.
In connfiguration mode you can set options that apply system-wide, also refered to as "global configurations." For instance, it is a good idea to name your router so that you can easily identify it. You do this in configuration mode with the hostname command.

Router(config)#hostname ExampleName
ExampleName(config)#

As demonstrated above, when you set the name of the host with the hostname command, the prompt immediately changes by replacing Router with ExampleName. (Note: It is a good idea to name your routers with an organized naming scheme.)
Another useful command issued from config mode is the command to designate the DNS server to be used by the router:

ExampleName(config)#ip name-server aa.bb.cc.dd
ExampleName(config)#ctrl-Z
ExampleName#

This is also where you set the password for privileged mode.

ExampleName(config)#enable secret examplepassword
ExampleName(config)#ctrl-Z
ExampleName#

Until you hit ctrl-Z (or type exit until you reach parent mode) your command has not been put into affect. You can enter config mode, issue several different commands, then hit ctrl-Z to activate them all. Each time you hit ctrl-Z you return to parent mode and the prompt:

ExampleName#

Here you use show commands to verify the results of the commands you issued in config mode. To verify the results of the ip name-server command, issue the command show host.

3.2 Configuring Cisco router interfaces

Cisco interface naming is straightforward. Individual interfaces are referred to by this convention:

media type slot#/port#

"Media type" refers to the type of media that the port is an interface for, such as Ethernet, Token Ring, FDDI, serial, etc. Slot numbers are only applicable for routers that provide slots into which you can install modules. These modules contain several ports for a given media. The 7200 series is an example. These modules are even hot-swapable. You can remove a module from a slot and replace it with a different module, without interrupting service provided by the other modules installed in the router. These slots are numbered on the router.
Port number refers to the port in reference to the other ports in that module. Numbering is left-to-right, and all numbering starts at 0, not at one.
For example, a Cisco 7206 is a 7200 series router with six slots. To refer to an interface that is the third port of an Ethernet module installed in the sixth slot, it would be interface ethernet 6/2. Therefor, to display the configuration of that interface you use the command:

ExampleName#show interface ethernet 6/2

If your router does not have slots, like a 1600, then the interface name consists only of:

media type port#

For example:

ExampleName#show interface serial 0

Here is an example of configuring a serial port with an IP address:

ExampleName#config
ExampleName(config)#interface serial 1/1
ExampleName(config-if)#ip address 192.168.155.2 255.255.255.0
ExampleName(config-if)#no shutdown
ExampleName(config-if)#ctrl-Z
ExampleName#

Then to verify configuration:

ExampleName#show interface serial 1/1

Note the no shutdown command. An interface may be correctly configured and physically connected, yet be "administratively down." In this state it will not function. The command for causing an interface to be administratively down is shutdown.

ExampleName(config)#interface serial 1/1
ExampleName(config-if)#shutdown
ExampleName(config-if)#ctrl-Z
ExampleName#show interface serial 1/1

In the Cisco IOS, the way to reverse or delete the results of any command is to simply put no infront of it. For instance, if we wanted to unassign the IP address we had assigned to interface serial 1/1:

ExampleName(config)#interface serail 1/1
ExampleName(config-if)#no ip address 192.168.155.2 255.255.255.0
ExampleName(config-if)ctrl-Z
ExampleName#show interface serial 1/1

Configuring most interfaces for LAN connections might consist only of assigning a network layer address and making sure the interface is not administratively shutdown. It is usually not necessary to stipulate data-link layer encapsulation. Note that it is often necessary to stipulate the appropriate data-link layer encapsulation for WAN connections, such as frame-relay and ATM. Serial interfaces default to using HDLC. A discussion of data-link protocols is outside the scope of this document. You will need to look up the IOS command encapsulation for more details.

3.3 Configuring Cisco Routing

IP routing is automatically enabled on Cisco routers. If it has been previously disabled on your router, you turn it back on in config mode with the command ip routing.

ExampleName(config)#ip routing
ExampleName(config)#ctrl-Z

There are two main ways a router knows where to send packets. The administrator can assign static routes, or the router can learn routes by employing a dynamic routing protocol.
These days static routes are generally used in very simple networks or in particular cases that necessitate their use. To create a static route, the administrator tells the router operating system that any network traffic destined for a specified network layer address should be forwarded to a similiarly specified network layer address. In the Cisco IOS this is done with the ip route command.

ExampleName#config
ExampleName(config)#ip route 172.16.0.0 255.255.255.0 192.168.150.1
ExampleName(config)#ctrl-Z
ExampleName#show ip route

Two things to be said about this example. First, the packet destination address must include the subnet mask for that destination network. Second, the address it is to be forwarded to is the specified addres of the next router along the path to the destination. This is the most common way of setting up a static route, and the only one this document covers. Be aware, however, that there are other methods.
Dynamic routing protocols, running on connected routers, enable those routers to share routing information. This enables routers to learn the routes available to them. The advantage of this method is that routers are able to adjust to changes in network topologies. If a route is physically removed, or a neighbor router goes down, the routing protocol searches for a new route. Routing protocols can even dynamically choose between possible routes based on variables such as network congestion or network reliability.
There are many different routing protocols, and they all use different variables, known as "metrics," to decide upon appropriate routes. Unfortunately, a router needs to be running the same routing protocols as its neighbors. Many routers can, however, run mutliple protocols. Also, many protocols are designed to be able to pass routing information to other routing protocols. This is called "redistribution." The author has no experience with trying to make redistribution work. There is an IOS redistribute command you can research if you think this is something you need. This document's compagnion case study describes an alternative method to deal with different routing protocols in some circumstances.
Routing protocols are a complex topic and this document contains only this superficial description of them. There is much to learn about them, and there are many sources of information about them available. An excelent source of information on this topic is Cisco's website, http://www.cisco.com.
This document describes how to configure the Routing Information Protocol (RIP) on Cisco routers. From the command-line, we must explicitly tell the router which protocol to use, and what networks the protocol will route for.

ExampleName#config
ExampleName(config)#router rip
ExampleName(config-router)#network aa.bb.cc.dd
ExampleName(config-router)#network ee.ff.gg.hh
ExampleName(config-router)#ctrl-Z
ExampleName#show ip protocols

Now when you issue the show ip protocols command, you should see an entry describing RIP configuration.

3.4 Saving your Cisco Router configuration

Once you have configured routing on the router, and you have configured individual interfaces, your router should be capable of routing traffic. Give it a few moments to talk to its neighbors, then issue the commands show ip route and show ip arp. There should now be entries in these tables learned from the routing protocol.
If you turned the router off right now, and turned it on again, you would have to start configuration over again. Your running configuration is not saved to any perminent storage media. You can see this configuration with the command show running-config.

ExampleName#show running-config

You do want to save your successful running configuration. Issue the command copy running-config startup-config.

ExampleName#copy running-config startup-config

Your configuration is now saved to non-volatile RAM (NVRAM). Issue the command show startup-config.

ExampleName#show startup-config

Now any time you need to return your router to that configuration, issue the command copy startup-config running-config.

ExampleName#copy startup-config running-config

3.5 Example Cisco Router configuration

Router>enable
Router#config
Router(config)#hostname N115-7206
N115-7206(config)#interface serial 1/1
N115-7206(config-if)ip address 192.168.155.2 255.255.255.0
N115-7206(config-if)no shutdown
N115-7206(config-if)ctrl-z
N115-7206#show interface serial 1/1
N115-7206#config
N115-7206(config)#interface ethernet 2/3
N115-7206(config-if)#ip address 192.168.150.90 255.255.255.0
N115-7206(config-if)#no shutdown
N115-7206(config-if)#ctrl-z
N115-7206#show interface ethernet 2/3
N115-7206#config
N115-7206(config)#router rip
N115-7206(config-router)#network 192.168.155.0
N115-7206(config-router)#network 192.168.150.0
N115-7206(config-router)#ctrl-z
N115-7206#show ip protocols
N115-7206#ping 192.168.150.1
N115-7206#config
N115-7206(config)#ip name-server 172.16.0.10
N115-7206(config)#ctrl-z
N115-7206#ping archie.au
N115-7206#config
N115-7206(config)#enable secret password
N115-7206(config)#ctrl-z
N115-7206#copy running-config startup-config
N115-7206#exit

4. Troubleshooting your Cisco router

Inevitably, there will be problems. Usually, it will come in the form of a user notifying you that they can not reach a certain destination, or any destinattion at all. You will need to be able to check how the router is attempting to route traffic, and you must be able to track down the point of failure.
You are already familiar with the show commands, both specific commands and how to learn what other show commands are available. Some of the most basic, most useful commands you will use for troubleshooting are:

ExampleName#show interfaces
ExampleName#show ip protocols
ExampleName#show ip route
ExampleName#show ip arp

4.1 Testing connectivity

It is very possible that the point of failure is not in your router configuration, or at your router at all. If you examine your router's configuration and operation and everything looks good, the problem might be be farther up the line. In fact, it may be the line itself, or it could be another router, which may or may not be under your administration.
One extremely useful and simple diagnostic tool is the ping command. Ping is an implementation of the IP Message Control Protocol (ICMP). Ping sends an ICMP echo request to a destination IP address. If the destination machine receives the request, it responds with an ICMP echo response. This is a very simple exchange that consists of:
Hello, are you alive?
Yes, I am.

ExampleName#ping xx.xx.xx.xx

If the ping test is successful, you know that the destination you are having difficulty reaching is alive and physically reachable.
If there are routers between your router and the destination you are having difficulty reaching, the problem might be at one of the other routers. Even if you ping a router and it responds, it might have other interfaces that are down, its routing table may be corrupted, or any number of other problems may exist.
To see where packets that leave your router for a particular destination go, and how far, use the trace command.

ExampleName#trace xx.xx.xx.xx

It may take a few minutes for this utility to finish, so give it some time. It will display a list of all the hops it makes on the way to the destination.

Monday, January 31, 2011

An Introduction to IP Addressing

Ways of Communication

Unicasting

· Communication between two devices is one-on-one. Create least traffic while communicating. Best in when one device want to communicate with one device only as no extra bothering the other hosts on the segment. Cannot be use in one-on-many devices to communicate as one hub device need to send the many copies of the same packet to all the hosts and will get the Acks from them.

Broadcasting

· Communication between two devices is one-on-all. One-n-all means all the host in the network on the same switch. When host send the packet on broadcast address then the switch will duplicate the packet and will send it on all the host in the network.

Multicasting

· Communication with one-on-one and one-on-many has too many limitations like large traffic to handle and security breach. It is used when one-on-group one way communication is required. For example live telecasting of video stream on internet, in this case the users are group of people who may need the particular stream but not all the hosts. So the user will join the particular multicast group to get that particular stream.

IP Addressing

One of the most important topics in any discussion of TCP/IP is IP addressing. An IP address is a numeric identifier assigned to each machine on an IP network. It designates the location of a device on the network. An IP address is a software address, not a hardware address—the latter is hardcoded on a network interface card (NIC) and used for finding hosts on a local network. IP addressing was designed to allow a host on one network to communicate with a host on a different network, regardless of the type of LANs the hosts is participating in.

IP stands for Internet Protocol, it's a communications protocol used from the smallest private network to the massive global Internet. An IP address is a unique identifier given to a single device on an IP network. The IP address consists of a 32-bit number that ranges from 0 to 4294967295. This means that theoretically, the Internet can contain approximately 4.3 billion unique objects. But to make such a large address block easier to handle, it was chopped up into four 8-bit numbers, or "octets," separated by a period. Instead of 32 binary base-2 digits, which would be too long to read, it's converted to four base-256 digits. Octets are made up of numbers ranging from 0 to 255. The numbers below show how IP addresses increment.

0.0.0.0
0.0.0.1
...increment 252 hosts...

0.0.0.254
0.0.0.255
0.0.1.0
0.0.1.1
...increment 252 hosts..

0.0.1.254
0.0.1.255
0.0.2.0
0.0.2.1
...increment 4+ billion hosts...

255.255.255.255

IP Terminology

Here are a few of the most important terms: -

Bit One digit; either a 1 or a 0.

Byte 8 bits.

Octet Always 8 bits. Base-8 addressing scheme.

Network address The designation used in routing to send packets to a remote network, for example, 10.0.0.0, 172.16.0.0, and 192.168.10.0.

Broadcast address

Used by applications and hosts to send information to all nodes on a network. Examples include 255.255.255.255, which is all networks, all nodes; 172.16.255.255, which is all subnets and hosts on network 17.16.0.0; and 10.255.255.255, which broadcasts to all subnets and hosts on network 10.0.0.0.

The Hierarchical IP Addressing Scheme

An IP address consists of 32 bits of information. These bits are divided into four sections, referred to as octets or bytes, each containing 1 byte (8 bits).

You can depict an IP address using one of three methods:

· Dotted-decimal, as in 172.16.30.56

· Binary, as in 10101100.00010000.00011110.00111000

· Hexadecimal, as in 82 39 1E 38

Network Addressing

The network address uniquely identifies each network. Every machine on the same network shares that network address as part of its IP address. In the IP address 172.16.30.56, for example, 172.16 is the network address.

The node address is assigned to, and uniquely identifies, each machine on a network. This part of the address must be unique because it identifies a particular machine—an individual—as opposed to a network, which is a group. This number can also be referred to as a host address. In the sample IP address 172.16.30.56, .30.56 is the node address. The designers of the Internet decided to create classes of networks based on network size. For the small number of networks possessing a very large number of nodes, they created the rank Class A network. At the other extreme is the Class C network, which is reserved for the numerous networks with a small number of nodes. The class distinction for networks between very large and very small is predictably called the Class B network. Subdividing an IP address into a network and node address is determined by the class designation of one’s network.

Figure summarizes the three classes of networks: -

Network Address Range: Class A

The designers of the IP address scheme said that the first bit of the first byte in a Class A network address must always be off, or 0. This means a Class A address must be between 0 and 127.

Here is how those numbers are defined:

0xxxxxxx: If we turn the other 7 bits all off and then turn them all on, we will find your Class A range of network addresses.

00000000=0

01111111=127

Network Address Range: Class B

In a Class B network, the RFCs state that the first bit of the first byte must always be turned on, but the second bit must always be turned off. If you turn the other six bits all off and then all on, you will find the range for a Class B network:

10000000=128

10111111=191

As you can see, this means that a Class B network can be defined when the first byte is configured from 128 to 191.

Network Address Range: Class C

For Class C networks, the RFCs define the first two bits of the first octet always turned on, but the third bit can never be on. Following the same process as the previous classes, convert from binary to decimal to find the range.

Here is the range for a Class C network:

11000000=192

11011111=223

So, if you see an IP address that starts at 192 and goes to 223, you’ll know it is a Class C IP address.

Network Address Ranges: Classes D and E

The addresses between 224 and 255 are reserved for Class D and E networks.

Class D is used for multicast addresses and Class E for scientific purposes.

Network Addresses: Special Purpose

Some IP addresses are reserved for special purposes, and network administrators shouldn’t assign these addresses to nodes. Table given bellow lists the members of this exclusive little club and why they’re included in it.

Network –Id

· Can be defined as the Id to represent the no. of host addresses in the same network in the topology. Cannot be assign to any host in the network. When all the host past is zero then it is called network-id. Or simply the first address of the network is always Network-Id

Broadcast-Id

· Address on which if packets are send these will be receive by all the hosts in the network. T his address is used when all the host in the network are suppose to get the same message. Cannot be assign to any host in the network. When all the host bits are one then it is called broadcast-id. Simply the last address of the network is called broadcast-id.

Class A Addresses

In a Class A network address, the first byte is assigned to the network address and the three remaining bytes are used for the node addresses. The Class A format is Network.Node.Node.Node For example, in the IP address 49.22.102.70, 49 is the network address, and 22.102.70 is the node address. Every machine on this particular network would have the distinctive network address of 49. Class A addresses are one byte long, with the first bit of that byte reserved and the seven remaining bits available for manipulation. As a result, the maximum number of Class A networks that can be created is 128. Why?

Because each of the seven bit positions can either be a 0 or a 1, thus 27 or 128.

To complicate matters further, the network address of all 0s (0000 0000) is reserved to designate the default route. Additionally, the address 127, which is reserved for diagnostics, can’t be used either, which means that you can only use the numbers 1 to 126 to designate Class A network addresses. This means the actual number of usable Class A network addresses is 128 minus 2, or 126. Got it? Each Class A address has three bytes (24-bit positions) for the node address of a machine. Thus, there are 224—or 16,777,216—unique combinations and, therefore, precisely that many possible unique node addresses for each Class A network. Because addresses with the two patterns of all 0s and all 1s are reserved, the actual maximum usable number of nodes for a Class A network is 224 minus 2, which equals 16,777,214.

Class A Valid Host IDs

Here is an example of how to figure out the valid host IDs in a Class A network address: 10.0.0.0 All host bits off is the network address. 10.255.255.255 All host bits on is the broadcast address. The valid hosts are the number in between the network address and the broadcast address: 10.0.0.1 through 10.255.255.254. Notice that 0s and 255s are valid host IDs. All you need to remember when trying to find valid host addresses is that the host bits cannot all be turned off or on at the same time.

Class B Addresses

In a Class B network address, the first two bytes are assigned to the network address, and the remaining two bytes are used for node addresses. The format is Network. Network. Node. Node. For example, in the IP address 172.16.30.56, the network address is 172.16, and the node address is 30.56. With a network address being two bytes (eight bits each), there would be 216 unique combinations. But the Internet designers decided that all Class B network addresses should start with the binary digit 1, then 0. This leaves 14 bit positions to manipulate, therefore 16,384 (214) unique Class B network addresses. A Class B address uses two bytes for node addresses. This is 216 minus thetwo reserved patterns (all 0s and all 1s), for a total of 65,534 possible node addresses for each Class B network.

Class B Valid Host IDs

Here is an example of how to find the valid hosts in a Class B network: 172.16.0.0 All host bits turned off is the network address.172.16.255.255 All host bits turned on is the broadcast address. The valid hosts would be the numbers in between the network address and the broadcast address: 172.16.0.1 through 172.16.255.254.

Class C Addresses

The first three bytes of a Class C network address are dedicated to the network portion of the address, with only one measly byte remaining for the node address. The format is Network.Network.Network.Node. Using the example IP address 192.168.100.102, the network address is192.168.100, and the node address is 102.In a Class C network address, the first three bit positions are always the binary 110. The calculation is such: 3 bytes, or 24 bits, minus 3 reserved positions, leaves 21 positions. Hence, there are 221, or 2,097,152, possible Class C networks. Each unique Class C network has one byte to use for node addresses. This leads to 28 or 256, minus the two reserved patterns of all 0s and all 1s, for a total of 254 node addresses for each Class C network.

Class C Valid Host IDs

Here is an example of how to find a valid host ID in a Class C network: 192.168.100.0 All host bits turned off is the network ID.192.168.100.255 All host bits turned on is the broadcast address. The valid hosts would be the numbers in between the network address and the broadcast address: 192.168.100.1 through 192.168.100.254

So while assigning IP addresses to host, two addresses can never assign one Network-Id and other is Broadcast-Id. Always subtract 2 from the total no of IPs in the network.

Network	Subnet-mask	Total No. of IPs	Usable IPs	Network –Id Broadcast-Id
10.0.0.0	255.0.0.0	2^24	2^24 - 2	10.0.0.0 / 10.255.255.255
172.31.0.0	255.255.0.0	65536	65534	172.31.0.0 / 172.31.255.255
192.168.0.0	255.255.255.0	256	254	192.168.0.0 / 192.168.0.1

Subnetting

The word subnet is short for sub network--a smaller network within a larger one. The smallest subnet that has no more subdivisions within it is considered a single "broadcast domain," which directly correlates to a single LAN (local area network) segment on an Ethernet switch. The broadcast domain serves an important function because this is where devices on a network communicate directly with each other's MAC addresses, which don't route across multiple subnets, let alone the entire Internet. MAC address communications are limited to a smaller network because they rely on ARP broadcasting to find their way around, and broadcasting can be scaled only so much before the amount of broadcast traffic brings down the entire network with sheer broadcast noise. For this reason, the most common smallest subnet is 8 bits, or precisely a single octet, although it can be smaller or slightly larger.

Subnetting is just the concept of borrowing the bits from the host part to reduce the host part and to include it in the network part. With this the no. of available network will be increase and the no of hosts the subnetted will be decreased. This way more efficient assignment of IP addressing in the network is possible with least possible wasting of IPs as they very limited in no .in IPv4

Subnets have a beginning and an ending, and the beginning number is always even and the ending number is always odd. The beginning number is the "Network ID" and the ending number is the "Broadcast ID." You're not allowed to use these numbers because they both have special meaning with special purposes. The Network ID is the official designation for a particular subnet, and the ending number is the broadcast address that every device on a subnet listens to.

With the Subnetting one bigger network can break down into smaller no. of Sub networks. With each sub network they must have their own Network-Id and Broadcast-Id.

For example

192.168.1.0 255.255.255.0

Network-Id 192.168.0.0 Broadcast-Id 192.168.0.255

By doing binary of last octet we will get following

192.168.0.00000000

Now here we have last 8 digits as host bits and first 24 bits are for network and are reserve.

Lets we have N no. of requirement of IP addresses

Now we have to find out how many bits are suppose to require to reserve for hosts and rest left bits are subnet bits

With N no. of hosts we require one Network-Id and Broadcast-Id so total no. of IPs required are

N + 2. To generate N options we need M(say) bits to reserve for network.

N + 2 ≤ 2^M (General for all classes)

Now the No. of Subnet Networks will be as given below

2^ (8-M)

Considering the requirement of 60 people

No. of Ips required are N + 2 = 62 where N = 60

By putting the values we will get M = 6

So no of Subnets will be 2^(8-6) = 4

And no. of people in the each subnet will be is 2^6 = 64

192.168.0. 00 000000

Subnet bits Host bits

Now Ist will be

192.168.0.00 ****** Decimal Form 192.168.0.0

192.168.0.01 ****** Decimal Form 192.168.0.64

192.168.0.10 ****** Decimal Form 192.168.0.128

192.168.0.11 ****** Decimal Form 192.168.0.192

Network-Id Broadcast-Id Network-Id Broadcast- Id

Decimal Form

192.16 8.0.00000000 192.168.0.00111111 192.168.0.0 192.168.0.63

192.168.0.01000000 192.168.0.01111111 192.168.0.64 192.168.127

192.168.0.10000000 192.168.0.10111111 192.168.0.128 192.168.0.191

192.168.0.11000000 192.168.0.11111111 192.168.0.192 192.168.0.255

IP Variable Length Subnet Masking (VLSM)

Conventional Subnet masking replaces the two-level IP addressing scheme with a more flexible three-level method. Since it lets network administrators assign IP addresses to hosts based on how they are connected in physical networks, subnetting is a real breakthrough for those maintaining large IP networks. It has its own weaknesses though, and still has room for improvement. The main weakness of conventional subnetting is in fact that the subnet ID represents only one additional hierarchical level in how IP addresses are interpreted and used for routing.

The Problem With Single-Level Subnetting

It may seem “greedy” to look at subnetting and say “what, only one additional level”? J However, in large networks, the need to divide our entire network into only one level of subnetworks doesn't represent the best use of our IP address block. Furthermore, we have already seen that since the subnet ID is the same length throughout the network, we can have problems if we have subnetworks with very different numbers of hosts on them—the subnet ID must be chosen based on whichever subnet has the greatest number of hosts, even if most of subnets have far fewer. This is inefficient even in small networks, and can result in the need to use extra addressing blocks while wasting many of the addresses in each block.

For example, consider a relatively small company with a Class C network, 201.45.222.0/24. They have six subnetworks in their network. The first four subnets (S1, S2, S3 and S4) are relatively small, containing only 10 hosts each. However, one of them (S5) is for their production floor and has 50 hosts, and the last (S6) is their development and engineering group, which has 100 hosts.

The total number of hosts needed is thus 196. Without subnetting, we have enough hosts in our Class C network to handle them all. However, when we try to subnet, we have a big problem. In order to have six subnets we need to use 3 bits for the subnet ID. This leaves only 5 bits for the host ID, which means every subnet has the identical capacity of 30 hosts. This is enough for the smaller subnets but not enough for the larger ones. The only solution with conventional subnetting, other than shuffling the physical subnets, is to get another Class C block for the two big subnets and use the original for the four small ones. But this is expensive, and means wasting hundreds of IP addresses.