Bits:                1     2      3        4      5        6      7      8
Mul Octet:    128   64    32      16     8        4      2      1
Sub Mask:   128  192   224    240  248   252   254  255
Wild Mask:   127    63    31      15     7       3       1     0

The number of bits determine the multiple of the octet.

SUBNETS:

255.255.255.224 is multiples of 32 in the last octet.

  Subnet                  Broadcast
  204.10.20.0/27      204.10.20.31
  204.10.20.32/27    204.10.20.63
  04.10.20.64/27      204.10.20.95
  etc…

255.255.248.0 is multiples of 8 in the third octet.

  Subnet                   Broadcast
  144.251.8.0/21      144.251.15.255
  144.251.16.0/21    144.251.23.255
  144.251.24.0/21    144.251.31.255
   etc…

VLMS (A multiple of 32 can be divided into 4 multiples of

  204.10.20.0/27
  204.10.20.32/27 = 204.10.20.32/29
                    204.10.20.40/29
                    204.10.20.48/29
                    204.10.20.56/29
  204.10.20.64/27
  204.10.20.96/27
  etc

ROUTE SUMMARIZATION (4 subnets in the summary route.)

  144.251.12.0/22 = 144.251.12.0/24
                    144.251.13.0/24
                    144.251.14.0/24
                    144.251.15.0/24

SUPER NETTING (4 networks in the summary route.)

  204.251.12.0/22 = 204.251.12.0/24
                    204.251.13.0/24
                    204.251.14.0/24
                    204.251.15.0/24

WILDCARD MASKS

  Wild card masks are the inverse of subnet masks on contiguous subnets

  255   255     255
 -128 -192   -224  etc…
===== ====    ====
  127     63        31