IP Address Conventions

You can use IPv4 Classless Inter-Domain Routing (CIDR) notation and the similar IPv6 prefix length notation to define address blocks in many places in the system.

When you use CIDR or prefix length notation to specify a block of IP addresses, the system uses only the portion of the network IP address specified by the mask or prefix length. For example, if you type 10.1.2.3/8, the system uses 10.0.0.0/8.

In other words, although Cisco recommends the standard method of using a network IP address on the bit boundary when using CIDR or prefix length notation, the system does not require it.