2 minutes
Sources:
- RFC 1519 (1993) – Classless Inter-Domain Routing (CIDR)
- RFC 1878 (1995) – Variable Length Subnet Table For IPv4
#net bits (CIDR) | netmask | # hosts (hb^2) | “size” | Cisco ACL wildcard mask | hex netmask |
---|---|---|---|---|---|
/0 | 0.0.0.0 | 4,294,967,296 | The Internet:-) | 255.255.255.255 | 00.00.00.00 |
/1 | 128.0.0.0 | 2,147,483,648 | 128A | 127.255.255.255 | 80.00.00.00 |
/2 | 192.0.0.0 | 1,073,741,824 | 64A | 63.255.255.255 | C0.00.00.00 |
/3 | 224.0.0.0 | 536,870,912 | 32A | 31.255.255.255 | F0.00.00.00 |
/4 | 240.0.0.0 | 268,435,456 | 16A | 15.255.255.255 | F8.00.00.00 |
/5 | 248.0.0.0 | 134,217,728 | 8A | 7.255.255.255 | FC.00.00.00 |
/6 | 252.0.0.0 | 67,108,864 | 4A | 3.255.255.255 | FE.00.00.00 |
/7 | 254.0.0.0 | 33,554,432 | 2A | 1.255.255.255 | FF.00.00.00 |
/8 | 255.0.0.0 | 16,777,216 | 1A | 0.255.255.255 | FF.80.00.00 |
/9 | 255.128.0.0 | 8,388,608 | 128B | 0.127.255.255 | FF.C0.00.00 |
/10 | 255.192.0.0 | 4,194,304 | 64B | 0.63.255.255 | FF.E0.00.00 |
/11 | 255.224.0.0 | 2,097,152 | 32B | 0.31.255.255 | FF.F0.00.00 |
/12 | 255.240.0.0 | 1,048,576 | 16B | 0.15.255.255 | FF.F8.00.00 |
/13 | 255.248.0.0 | 524,288 | 8B | 0.7.255.255 | FF.FC.00.00 |
/14 | 255.252.0.0 | 262,144 | 4B | 0.3.255.255 | FF.FE.00.00 |
/15 | 255.254.0.0 | 131,072 | 2B | 0.1.255.255 | FF.FF.00.00 |
/16 | 255.255.0.0 | 65,536 | 1B | 0.0.255.255 | FF.FF.80.00 |
/17 | 255.255.128.0 | 32,768 | 128C | 0.0.127.255 | FF.FF.C0.00 |
/18 | 255.255.192.0 | 16,384 | 64C | 0.0.63.255 | FF.FF.E0.00 |
/19 | 255.255.224.0 | 8192 | 32C | 0.0.31.255 | FF.FF.F0.00 |
/20 | 255.255.240.0 | 4096 | 16C | 0.0.15.255 | FF.FF.F8.00 |
/21 | 255.255.248.0 | 2048 | 8C | 0.0.7.255 | FF.FF.FC.00 |
/22 | 255.255.252.0 | 1024 | 4C | 0.0.3.255 | FF.FF.FE.00 |
/23 | 255.255.254.0 | 512 | 2C | 0.0.1.255 | FF.FF.FF.00 |
/24 | 255.255.255.0 | 256 | 1C | 0.0.0.255 | FF.FF.FF.80 |
/25 | 255.255.255.128 | 128 | 1/2C | 0.0.0.127 | FF.FF.FF.C0 |
/26 | 255.255.255.192 | 64 | 1/4C | 0.0.0.63 | FF.FF.FF.E0 |
/27 | 255.255.255.224 | 32 | 1/8C | 0.0.0.31 | FF.FF.FF.F0 |
/28 | 255.255.255.240 | 16 | 1/16C | 0.0.0.15 | FF.FF.FF.F8 |
/29 | 255.255.255.248 | 8 | 1/32C | 0.0.0.7 | FF.FF.FF.FC |
/30 | 255.255.255.252 | 4 | 1/64C | 0.0.0.3 | FF.FF.FF.FE |
/31 | 255.255.255.254 | PtoP links only | 1/128C | FF.FF.FF.FF | |
/32 | 255.255.255.255 | This is a single host route(usehostnotation) | |||