Apr 282011
 
#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)
Sources:
RFC 1519 (1993) — Classless Inter-Domain Routing (CIDR)
RFC 1878 (1995) — Variable Length Subnet Table For IPv4