T171 - TCP/IP Subnets
Network administrators often segment networks using devices such as routers in order to reduce network traffic. On routed networks, administrators need a way to subdivide the network into smaller subnetworks (called subnets) and impose a hierarchical design so that a message can travel efficiently to its destination. TCP/IP provides this subnetting capability through logical addressing . A logical address is an address configured through the network software. In TCP/IP a computer's logical address is called an IP address and can include:
A network ID number, identifying a network.
A subnet ID number, identifying a subnet on the network.
A host ID number, identifying the computer on the subnet.
The IP addressing system also lets the network administrator impose a sensible numbering scheme on the network so that the progression of addresses reflects the internal organisation of the network.