1. Address Classification
2. Broadcast address
3. Multicast address
4. Subnet Mask
The network is divided into four types of ABCD. The subnet mask is equivalent to subdividing the host identification part on the basis of classification, which is equivalent to extending the network identification part, so that the host identification under one type of network is subdivided into different sub Network
Network address: set all host IDs to 0
Broadcast address: set all host IDs to 1
5. Global address and private address
