Backbone Routers

Backbone routers are responsible for maintaining topology information for the backbone as well as for propagating summarized topology information for each of the other areas within the autonomous system.

Figure 12-8 illustrates the exchange of LSAs by a backbone router.

Figure 12-8: Intra-area LSA flooding in an OSPF network by backbone routers.

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Figure 12-8: Intra-area LSA flooding in an OSPF network by backbone routers.

Although the distinctions between backbone, area border, and internal area routers may seem clear and distinct, there is room for confusion because of the capability of the router to support multiple I/O port connections to other routers. Each port, in theory, could be connected to a different area. Consequently, the router forms a border between the various areas to which its interface ports connect.

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