IP Networking

In the IP addresses 193.32.156.0/24 and 169.183.0.0/16, what do the /16 and /24 represent?

The network mask. /24 implies 255.255.255.0, and /16 implies 255.255.0.0. It's equivalent to stripping 32-n bits off the right of a 255.255.255.255 netmask.

So 172.16.0.0/16 means the entire 192.168.x.x subnet, 192.168.1.0/24 means the entire 192.168.1.x subnet, and so forth.

This notation is known as IPv4 CIDR notation. CIDR specifies an IP address range using a combination of an IP address and its associated network mask. CIDR notation uses the following format:

Code:

xxx.xxx.xxx.xxx/n

where n is the number of leftmost 1 bits in the mask.

It represents the amount of bits given to the network in binary terms. By masking those bits in binary form, the remaindering bits will represent the possible host identities.

Thanks all

An IPv4 address contains 4 octets i.e. 32 bits. ip addresses are divided into 4 classes depending upon how many bits in 32 bits represent the network address and how many bits represent the host address.

for instance the class A ip address has the first 8 bits represent the network address and rest 24 bits represent the host address.

A network mask is the one which helps you finding which part in 32 bits represents the network address. Say for class A the network mask is 255.0.0.0

So in general a class A ip address can be represented as 1.2.3.4 255.0.0.0

There is another concept called as sub-netting which makes use of some bits in the host part for network address. Sub-netting allows you to create multiple logical networks inside classes of networks.

for example we can create an IP subnet for class A by using 3 bits of 24 host bits for network address. In this case the first 11 bits of 32 represent the network address and the reset 21 bits represent the host address.

In such cases the class A address can be represented as 1.2.3.4 255.224.0.0

The above representation is called as address/mask representation.. There is another representation know as CIDR (Classless inter-domain routing) which represents the ip address irrespective of class, but represents the number of bits used for network address.

In the CIDR representation the ip address in the above example is represented as 1.2.3.4/11 since 11 bits are used as mask.

so, in the representation of ip address 193.32.156.0/24 and 169.183.0.0/16, 24 and 16 represent the mask bits...so the above two addresses are class c and class b respectively.

Thanks,
Chaitanya.