Here are the charts, followed by some explanations of what they mean.
CIDR | SUBNET MASK | WILDCARD MASK | # OF IP ADDRESSES | # OF USABLE IP ADDRESSES |
---|---|---|---|---|
/32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 |
/31 | 255.255.255.254 | 0.0.0.1 | 2 | 2* |
/30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 |
/29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 |
/28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 |
/27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 |
/26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 |
/25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 |
/24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 |
/23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 |
/22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 |
/21 | 255.255.248.0 | 0.0.7.255 | 2,048 | 2,046 |
/20 | 255.255.240.0 | 0.0.15.255 | 4,096 | 4,094 |
/19 | 255.255.224.0 | 0.0.31.255 | 8,192 | 8,190 |
/18 | 255.255.192.0 | 0.0.63.255 | 16,384 | 16,382 |
/17 | 255.255.128.0 | 0.0.127.255 | 32,768 | 32,766 |
/16 | 255.255.0.0 | 0.0.255.255 | 65,536 | 65,534 |
/15 | 255.254.0.0 | 0.1.255.255 | 131,072 | 131,070 |
/14 | 255.252.0.0 | 0.3.255.255 | 262,144 | 262,142 |
/13 | 255.248.0.0 | 0.7.255.255 | 524,288 | 524,286 |
/12 | 255.240.0.0 | 0.15.255.255 | 1,048,576 | 1,048,574 |
/11 | 255.224.0.0 | 0.31.255.255 | 2,097,152 | 2,097,150 |
/10 | 255.192.0.0 | 0.63.255.255 | 4,194,304 | 4,194,302 |
/9 | 255.128.0.0 | 0.127.255.255 | 8,388,608 | 8,388,606 |
/8 | 255.0.0.0 | 0.255.255.255 | 16,777,216 | 16,777,214 |
/7 | 254.0.0.0 | 1.255.255.255 | 33,554,432 | 33,554,430 |
/6 | 252.0.0.0 | 3.255.255.255 | 67,108,864 | 67,108,862 |
/5 | 248.0.0.0 | 7.255.255.255 | 134,217,728 | 134,217,726 |
/4 | 240.0.0.0 | 15.255.255.255 | 268,435,456 | 268,435,454 |
/3 | 224.0.0.0 | 31.255.255.255 | 536,870,912 | 536,870,910 |
/2 | 192.0.0.0 | 63.255.255.255 | 1,073,741,824 | 1,073,741,822 |
/1 | 128.0.0.0 | 127.255.255.255 | 2,147,483,648 | 2,147,483,646 |
/0 | 0.0.0.0 | 255.255.255.255 | 4,294,967,296 | 4,294,967,294 |
* /31 is a special case detailed in RFC 3021 where networks with this type of subnet mask can assign two IP addresses as a point-to-point link.
And here’s a table of the decimal to binary conversions for subnet mask and wildcard octets:
SUBNET MASK | WILDCARD | ||
---|---|---|---|
0 | 00000000 | 255 | 11111111 |
128 | 10000000 | 127 | 01111111 |
192 | 11000000 | 63 | 00111111 |
224 | 11100000 | 31 | 00011111 |
240 | 11110000 | 15 | 00001111 |
248 | 11111000 | 7 | 00000111 |
252 | 11111100 | 3 | 00000011 |
254 | 11111110 | 1 | 00000001 |
255 | 11111111 | 0 | 00000000 |
Note that the wildcard is just the inverse of the subnet mask.