IPv4 Network Addresses

IPv4 Subnet Mask

To ensure that all hosts within a network are assigned a unique IP address within that network range, it is important to identify the first host address and the last host address. Hosts within a network can be assigned IP addresses within this range.

First Host Address

As seen in Figure 1, the host portion of the first host address will contain all 0 bits with a 1 bit for the lowest order or right-most bit. This address is always one greater than the network address. In this example the first host address on the 10.1.1.0/24 network is 10.1.1.1. It is common in many addressing schemes to use the first host address for the router or default gateway address.

Last Host Address

The host portion of the last host address will contain all 1 bits with a 0 bit for the lowest order or right-most bit. This address is always one less than the broadcast address. As seen in Figure 2, the last host address on the 10.1.1.0/24 network is 10.1.1.254.