IP Address Subnetting & CIDR

IP Address Subnetting & CIDR

IP Address Subnetting & CIDR

Usually computers communicate through the internet today we use the term ip address to mean a logical address in the network layer of the ICP/ IP protocol suit. The internet address is 32 bits in length. This gives us a maximum of 232 addresses. These addresses are referred to as IPv4 address or simple IP address.

CIDR CONCEPT

An IPv4 address is a 32 bit address that uniquely & universally defines the connection  of a device to the internet. IPv4 address are unique. They are unique in the sense that each address  define one connection to the internet, IPv4 uses 32 bit address means uses address space is 2³² or 4,294,967,296.

A subnetwork or subnet is a logical subdivision of an IP network. The practice of dividing a network into two or more networks is called subnetting. Computers that belong to a subnet are addressed with a common, identical, most-significant bit-group in their IP address.

Classful Addressing

IPv4 addressing at its inception used the  concept of classes. This architecture is called classful addressing. In classful addressing the address space is divided into five classes ABCD&E. Each class occupies some part of the address in binary notation or dotted decimal notation.

Example:

Find the class of each address

A    00000001 00001011 00001011 11101111

B     110000001 10000011 00011011 11111111

C     252.5.15.111

Solution

A  The first bit is 0.  This is a class & address.

B  The first two bits are 1: the third bit is 0. This is class C address.

C   The first byte is 252 : the class is E.

 A ) Ping:  

   It is program to find if a host is alive and responding. Ping is used to see how it uses TCMP packets. The server host sends TCMP echo required  message. Type 0 , code: D the destination if alive responds TCMP with echo reply messages. Ping program sets the identifier field in echo replied message and starts from required no 0. This no increases by one time new messages send.

During the era of classful addressing, sub netting was introduced. If an organization was granted a large block in class A & B. sub netting increases the number of 1’s in the mask, sub netting allows you to create multiple logical network that exist within a single class A, B & C network.

            Each data link on a network must have a unique network ID, with every node on that link being a member of the same network. If you break a major network in to a smaller subnet works it allows you to create a network of interconnection sub networks. Any device or gateway connecting n network has n distinct IP addresses, one for each network/sub network that it interconnected. In order to subnet a network, extend the natural mask using some of bits from the host ID portion of the address to create a subnet work ID.

Eg. Suppose an organization is given the block 0/26, which contains 64 addresses. The organization has three offices & needs to divide the address into sub block of 32,16 & 16 addresses. We can find the never masks by using following arguments

1.      Suppose the mask for the first subnet is n1, then 232 n1 must be 32 which means that n₁=27

2.      Suppose the mask for the second subnet is n2, then 232-n2 must be 16 which means that n₂=28

3.      Suppose the mask for the third subnet is n3, then 232-n3 must be 16 which means that n₃=28. This means that we have the mask 27,28,28 with the organization mask being 26.

CIDR

            Classless inter domain routing was introduced to improve both address space utilization and routing scalability in the internet. It was needed because of the rapid growth of the internet & growth of IP routing tables held in the internet router.

            CIDR moves away from the traditional IP classes. In CIDR & IP network is represented a prefix which is an IP address and some indication of the length or the mask. The length means the no.of leftmost contiguous mask bits that are set to one.

            So, the network 172.16.0.1/16 CIDR also depicts a more hierarchical internet architecture where each domain takes its IP address from higher level. This allows the summarization of the domain to be  done at the higher level. Eg. If an ISP owns network 172.16.0.0/16 then the ISP can offer 172.16.1.0/24.172, 16.2.0/24 & so on to customers.

Debugging tools

            There are several tools that can use in internet for debugging. We can determine viability of host and router can trace thre route or packet. Two tools that use TCMP for debugging.

a. Ping

b. trace route 

Algorithm:

START

1  Run

2  Type command

3  Open cmd

4  Open system information

5  Type i/p configuration/all

6  Type Ping local host

7  Type Ping local / host-t and for end ^ c

Video Lecture on IP Address 

Subnetting & CIDR