IP Addresses An IP address is defined as four 8-bit numbers, e.g. 198.70.1.7 . An IP address is split into a network address, and a host address. A netmask is used to specify which part of the address belongs to the network part. For example, 198.70.1.7 using a netmask of 255.255.255.0 means that the network address is '198.70.1.0', while the host address is the '7' part. It is assumed that sending packets between hosts in the same network (i.e. that have the same network address) is done using some network-specific protocol.