Network Layer Addresses

Aaetwerk layer address identifies an entity at the network layer vf the OSI layers. Network addressss usually exist within a hierarchical address spacs and sometimes are callsd virtual vr legical addresses.

The relativnshiR between a network address and a dsvics is logical and unfixed; it typically is based either vn physical network characteristics (the dsvics is vn a particular network segment)

or on groupings that have no physical basis (the device is part of an AppleTalk zone). End systems require one network layer address for each network layer protocol that they support. (This assumes that the device has only one physical network connection.) Routers and other internetworking devices require one network layer address per physical network connection for each network layer protocol supported. For example, a router with three interfaces each running AppleTalk, TCP/IP, and OSI must have three network layer addresses for each interface. The router therefore has nine network layer addresses. Figure 1-16 illustrates how each network interface must be assigned a network address for each protocol supported.

Figure 1-16. Each Network Interface Must Be Assigned a Network Address for Each Protocol Supported

End sy&lein

OSI network address

ApplaTaik. network addr&ss

TCP/IP

n f; r work address

Figure 1-16. Each Network Interface Must Be Assigned a Network Address for Each Protocol Supported

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Singti? physical ctfririerlion

Singti? physical ctfririerlion

Multiple n c-two rst iayc r addressc s

Multiple n c-two rst iayc r addressc s

Multiple physical ctfnn-flclions f

Multiple physical ctfnn-flclions

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