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Part 3

Bridges and Routers

Bridges and routers are used to expand beyond the confines of a single LAN.

Bridges are used for interconnection of LANs that use identical protocols at the MAC layer. Bridges are used for several reasons:

See figure 4.8, page 136. The bridge is attached to both LANs. The functions of the bridge are:

Design aspects:

See figure 4.9, page 138.


Routers connect dissimilar networks and operate on layer 3 of the OSI model, the network layer. Routers must cope with several issues:

Go through an IP routing example.

fig49ap138.gif (2548 bytes)

IEEE 802