Clasless Inter-Domain Routing (CIDR)

Clasless Inter-Domain Routing (CIDR)

Another term that you need to understand so well is Classless Inter-Domain Routing (CIDR). CIDR is basically the method used by ISPs (Internet Service Providers) to allocate a number of addresses in a company, home / office customers. ISP providing the address in block size (block size) -. certain

When you receive sebuahblok addresses from an ISP, what you received looks like: 192.168.10.32/28. What is from these numbers is to explain your subnet mask. Notation slash or slash notation (/) means how many bits of value 1 (in the example above is / 28, meaning there are 28-bit value 1).

We know that the maximum value after the slash is / 32 because a byte is 8 bits and there are 4 bytes in an IP address: (4 x 8 = 32). But you should bear in mind that the largest subnet mask available (regardless of class address) is just / 30, because you have to keep at least two bits as bits of the Host.

Take the example of a Class A subnet mask, which is 255.0.0.0. This means that the first byte of the subnet mask is all 1 or 11,111,111. If you look at the notation side, you need to count all the bits 1 to get his mask. 255.0.0.0 Mask with / 8 because it has 8 bits of value 1-or 8 bits are on.

Default mask is a class B is 255.255.0.0, which is equal to / 16 because its 16-bit is 1, namely: 11111111.11111111.00000000.00000000.

The following table contains a list of all the available subnet mask and CIDR slash notation which is equivalent to the subnet mask.