Configuring IP Addresses Using CIDR Notation
Use Classless Inter-Domain Routing (CIDR) notation when configuring IP addresses for IP range, IPsec, or GRE authentication and for web policies.
CIDR notation specifies:
- A routing prefix to a network
- An IP address or range on the specified network
CIDR syntax consists of an IPv4 or IPv6 address followed by a forward slash and a decimal number. The decimal number specifies the number of bits in the network prefix.
IPv4 network prefixes are allowed to range in size from 8 bits to 32 bits. A 24-bit IPv4 network prefix consists of 256 addresses. IPv6 network prefixes are allowed to range in size from 8 bits to 128 bits. A 120-bit IPv6 network prefix consists of 256 addresses.
| Protocol | Network prefix (bits) | CIDR notation (example) | Specified IP address range |
|---|---|---|---|
| IPv4 | 8-32 | 127.0.0.0/24 | From 127.0.0.0 to 127.0.0.255 |
| IPv6 | 8-128 | 2001:db8:1234:0:0:0:0:ff00/120 | From 2001:db8:1234:0:0:0:0:ff00 to 2001:db8:1234:0:0:0:0:ffff |