Subnetting Cheat Sheet

Subnetting Cheat Sheet For Quick Reference

Subnetting is a method of segmenting hosts within a network and providing additional structure hosts within a network and providing additional structure. Without subnets, an organization operates as a flat network. These flat topologies result in short routing tables, but as the network grows, the use of bandwidth becomes inefficient.

Classes	1st Octet Range	Network Bits	Possible Networks	Host Bits	No. of Hosts per Network
A	1-126	8	126	24	16,777,216
B	128-191	16	16,384	16	65,536
C	192-223	24	2,097,152	8	256

Note: The total number of available hosts on a network can be derived by using the formula 2^n-2, where n is the number of host bits. The -2 accounts for an octet with all 0s, which is reserved for network identification, and all 1s, which is reserved for sending a broadcast message to all hosts.