Sub-netting: Divide a network into 2 or more networks

Points to keep in mind:
1. Computers that belong to a subnet are addressed with an identical most-sig bit group in the IP addresses
2. IP is logically divided into NetworkIdentifier/Routingprefix and Restfield/HostIdentifier
3. Routing prefix can be expressed as CIDR (Classless Inter-Domain Routing) notation. Ex. 198.51.100.0/24
Implies
NetworkIdentifier has 24 bits allocated and Rest field has 8 bits allocated
4. A network is characterized by subnet mask or netmask, applied by bitwise AND operation
Ex. For 198.51.100.0/24, the subnet mask is 255.255.255.0
Subnet masks are used to identify the networks
*If 198.51.100.0 is NetworkIdentifier, then 198.51.100.255 is BroadcastIdentifier

For Class A, mask is 255.0.0.0; Class B, mask is 255.255.0.0; Class C, mask is 255.255.255.0

5. Traffic is exchanged between subnets through routers, when the routing prefixes of the source and destination addresses differ; A router serves as a logical boundary between the subnets.


Advantages:
1. Enhances routing efficiency
2. Enhanced control over network
3. Organization's network address space can be organized hierarchically

Source: Wikipedia