Why Masking?
Mask essentially gives the IP address for host zero on that subnet. (128.171.17.0)
This happens for the IP destination address in the packet being sent. (128.171.17.13 becomes 128.171.17.0)
This happens for the router’s own IP addresses (128.171.17.3 becomes 128.171.17.0)
It is easy for computers to compare two numbers for being equal or not equal
- 128.171.17.0 = 128.171.17.0