CIDR notation

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To set up networking, you need to know the IP address and netmask of your computer. One way to note a netmask is like this:

IP:, netmask:

With the CIDR notation, this goes easier. In this particular case it would be


The CIDR notation contains the IP address, then a slash ("/"), then the number of bits set in the subnet mask:


is an abbreviation for:

IP Address:
(in binary) 11111111.11111111.11111111.00000000

because this subnet mask uses 24 bits for the network portion of the address.

Another example:


would look like:

IP Address:
(in binary) 11111111.11111111.11111000.00000000

And so on...

Because of its versatility, brevity, and easiness to understand CIDR notation is now the preferred method of identifying a network.

See also