Network Masks
Indicate which portion of the address identifies the network and which portion identifies the node
Class A Mask
255.0.0.0
Class B
255.255.0.0
Class C
255.255.255.0
How do you know which portion of a mask is the network
The portion that is all 1s (I.e the 255s)
Subnetting
Allows you to create multiple logical networks that exist and use more than one network within a single class A/B/C network
Each data link on a network
Must have a unique network ID (every node on that link being on the same network)