wiki:Appendices/CIDRnotation

CIDR Notation

Whenever creating subnet based account in ArrowBilling, CIDR notation is used.

CIDR notation is constructed from the IP address and the prefix size, the latter being the number of leading 1 bits of the routing prefix. It is followed by a separator character, the forward slash (/) character, and the prefix size expressed as a decimal number.

The address may denote a single, distinct, interface address or the beginning address of an entire network. In the latter case the CIDR notation specifies the address block allocation of the network. The maximum size of the network is given by the number of addresses that are possible with the remaining, least-significant bits below the prefix.

Example CIDR subnet size chart:

CIDR Netmask Example Number of hosts in subnet
/8 255.0.0.0 10.0.0.0/8 = 10.0.0.0 - 10.255.255.255 16777216
/16 255.255.0.0 10.0.0.0/12 = 10.0.0.0 - 10.0.255.255 65536
/24 255.255.255.0 10.0.0.0/24 = 10.0.0.0 - 10.0.0.255 256
/25 255.255.255.128 10.0.0.0/25 = 10.0.0.0 - 10.0.0.127 128
/26 255.255.255.192 10.0.0.0/26 = 10.0.0.0 - 10.0.0.63 64
/27 255.255.255.224 10.0.0.0/27 = 10.0.0.0 - 10.0.0.31 32
/28 255.255.255.240 10.0.0.0/28 = 10.0.0.0 - 10.0.0.15 16
/29 255.255.255.248 10.0.0.0/29 = 10.0.0.0 - 10.0.0.7 8
/30 255.255.255.252 10.0.0.0/30 = 10.0.0.0 - 10.0.0.3 4
/31 255.255.255.254 10.0.0.0/31 = 10.0.0.0 - 10.0.0.1 2
/32 255.255.255.255 10.0.0.1/32 = 10.0.0.1 only 1
Last modified 7 years ago Last modified on Jan 24, 2011, 4:16:44 PM