This is less of a post and more of a CIDR to mask cheatsheet to remind me how many IPs I get for a given block.

CIDR Subnet Total IPs Usable IPs
/32 255.255.255.255 1 1
/31 255.255.255.254 2 0
/30 255.255.255.252 4 2
/29 255.255.255.248 8 6
/28 255.255.255.240 16 14
/27 255.255.255.224 32 30
/26 255.255.255.192 64 62
/25 255.255.255.128 128 126
/24 255.255.255.0 256 254
/23 255.255.254.0 512 510
/22 255.255.252.0 1,024 1,022
/21 255.255.248.0 2,048 2,046
/20 255.255.240.0 4,096 4,094
/19 255.255.224.0 8,192 8,190
/18 255.255.192.0 16,384 16,382
/17 255.255.128.0 32,768 32,766
/16 255.255.0.0 65,536 65,534
/15 255.254.0.0 131,072 131,070
/14 255.252.0.0 262,144 262,142
/13 255.248.0.0 524,288 524,286
/12 255.240.0.0 1,048,576 1,048,574
/11 255.224.0.0 2,097,152 2,097,150
/10 255.192.0.0 4,194,304 4,194,302
/9 255.128.0.0 8,388,608 8,388,606
/8 255.0.0.0 16,777,216 16,777,214
/7 254.0.0.0 33,554,432 33,554,430
/6 252.0.0.0 67,108,864 67,108,862
/5 248.0.0.0 134,217,728 134,217,726
/4 240.0.0.0 268,435,456 268,435,454
/3 224.0.0.0 536,870,912 536,870,910
/2 192.0.0.0 1,073,741,824 1,073,741,822
/1 128.0.0.0 2,147,483,648 2,147,483,646
/0 0.0.0.0 4,294,967,296 4,294,967,294
Are you confused about the ever growing number of services in AWS and Azure? Why not checkout these super useful glossaries that are always up to date!
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