Netmask Cheat Sheet

 

Netmask Netmask (binary) CIDR Notes 255.255.255.255 11111111.11111111.11111111.11111111 /32 Host (single addr) 255.255.255.254 11111111.11111111.11111111.11111110 /31 Unuseable 255.255.255.252 11111111.11111111.11111111.11111100 /30 2 useable 255.255.255.248 11111111.11111111.11111111.11111000 /29 6 useable 255.255.255.240 11111111.11111111.11111111.11110000 /28 14 useable 255.255.255.224 11111111.11111111.11111111.11100000 /27 30 useable 255.255.255.192 11111111.11111111.11111111.11000000 /26 62 useable 255.255.255.128 11111111.11111111.11111111.10000000 /25 126 useable 255.255.255.0 11111111.11111111.11111111.00000000 /24 "Class C" 254 useable 255.255.254.0 11111111.11111111.11111110.00000000 /23 2 Class C's 255.255.252.0 11111111.11111111.11111100.00000000 /22 4 Class C's 255.255.248.0 11111111.11111111.11111000.00000000 /21 8 Class C's 255.255.240.0 11111111.11111111.11110000.00000000 /20 16 Class C's 255.255.224.0 11111111.11111111.11100000.00000000 /19 32 Class C's 255.255.192.0 11111111.11111111.11000000.00000000 /18 64 Class C's 255.255.128.0 11111111.11111111.10000000.00000000 /17 128 Class C's 255.255.0.0 11111111.11111111.00000000.00000000 /16 "Class B" 255.254.0.0 11111111.11111110.00000000.00000000 /15 2 Class B's 255.252.0.0 11111111.11111100.00000000.00000000 /14 4 Class B's 255.248.0.0 11111111.11111000.00000000.00000000 /13 8 Class B's 255.240.0.0 11111111.11110000.00000000.00000000 /12 16 Class B's 255.224.0.0 11111111.11100000.00000000.00000000 /11 32 Class B's 255.192.0.0 11111111.11000000.00000000.00000000 /10 64 Class B's 255.128.0.0 11111111.10000000.00000000.00000000 /9 128 Class B's 255.0.0.0 11111111.00000000.00000000.00000000 /8 "Class A" 254.0.0.0 11111110.00000000.00000000.00000000 /7 252.0.0.0 11111100.00000000.00000000.00000000 /6 248.0.0.0 11111000.00000000.00000000.00000000 /5 240.0.0.0 11110000.00000000.00000000.00000000 /4 "Class E" (Multicast and reserved) 224.0.0.0 11100000.00000000.00000000.00000000 /3 192.0.0.0 11000000.00000000.00000000.00000000 /2 128.0.0.0 10000000.00000000.00000000.00000000 /1 0.0.0.0 00000000.00000000.00000000.00000000 /0 IP space