A network address is the first IPv4 address in a network. All bits in its host portion are 0, so it identifies the entire network and cannot be assigned to a host. section 7.3.3 section 7.4
Use these rules to identify a network address and distinguish it from nearby addresses:
- Read the prefix length or subnet mask to separate the network portion from the host portion. section 7.4
- Set every host bit to 0; the resulting first address is the network address. section 7.3.3
- Do not assign it to a host. The first usable host address is the next address, while the broadcast address has all host bits set to 1. section 7.3.3
- Remember that subnet network addresses do not always end in .0; subnet boundaries can occur within an octet. section 11.2.1
Common IPv4 examples
For 192.168.100.0/24, the network address is 192.168.100.0, the first usable address is 192.168.100.1, and the broadcast address is 192.168.100.255. When 192.168.1.0/24 is divided into /26 subnets, 192.168.1.64/26 has network address 192.168.1.64, usable range 192.168.1.65–192.168.1.126, and broadcast address 192.168.1.127.
