Each member network in a routed internetwork requires a unique identifier.
For devices to correctly communicate on a LAN, they must be uniquely identified by means of a data link identifier. If a routed internetwork—a network of networks—is to be created, then each member network must likewise be uniquely identifiable.
The most fundamental criterion for a routed internetwork is that for a router to correctly deliver packets to their proper destination, each and every network, or data link, must be uniquely identified. Providing this unique identification is the purpose of a network address.
Figure 1.10 suggests a type of network address. Notice that every network has its own unique address. Notice ...