I check for patterns...

Something I need to learn or work today.. Here's a cheatsheet for
identifying what
netmasks, hosts and subnets are equivalent to.

NETMASKS, HOSTS, SUBNETS
/30 255.255.255.252 = 4 hosts = 64 subnets
/29 255.255.255.248 = 8 hosts = 32 subnets
/28 255.255.255.240 = 16 hosts = 16 subnets
/27 255.255.255.224 = 32 hosts = 8 subnets
/26 255.255.255.192 = 64 hosts = 4subnets
/25 255.255.255.128 = 128 hosts = 2 subnets
/24 255.255.255.0 = 256hosts = 1 subnet
/23 255.255.254.0 = 512 hosts = 2subnets
/22 255.255.252.0 = 1024 hosts = 4 subnets
/20 255.255.248.0 = 2048 hosts = 8 subnets
/19 255.255.240.0 = 4096 hosts = 16 subnets
/18 255.255.224.0 = 8192 hosts = 32 subnets
/17 255.255.192.0 = 16384 hosts = 64 subnets
/16 255.255.128.0 = 32768 hosts = 128 subnets
/15 255.255.0.0 = 65536 hosts = 256 subnets

aside: Note these special numbers in the IPv4 world
256(=2^8), 255, 254, 252, 248,240, 224, 192, 128, 0