IP Subnets and Network Masks
Subnets provide extra flexibility to network administrators by subdividing IP networks into smaller subnetworks
IP subnets define two or more physical networks that share a common netid field (portion of 32-bit address that is assigned by the NIC)
Subnetting allows routers to hide complexity of multiple LANs from the rest of the Internet and Enterprise WANs (e.g. if IP address = 129.24.8.1 then Network = 129.24., Subnet = 8. to 15., Host = 1)