Summary

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OSPF is a link-state protocol. OSPF has five packets ‚ Hello, DBD, link-state request, link-state update, and link-state acknowledgment. These packets are used according to the state of adjacency . Several types of LSAs exist, the most common or which are router, network, summary, summary ASBR, external, and NSSA LSAs. OSPF has several area types, which are normal, stub, totally stub, NSSA, and totally NSSA. These areas can be used according to the network need. The most restricted form of area is a totally stubby area, in which the area relies on only the summary default route that it receives from the ABR.

OSPF can be run under several media types options ‚ multiaccess , point-to-point, NBMA, and demand circuit. In non ‚ fully meshed NBMA environments, the most recommended network type is point-to-multipoint. Point-to-multipoint nonbroadcast networks are useful only when the medium does not support the multicast capabilities. No DR or BDR is elected in this network type.

OSPF adjacencies go through several stages before they are formed. The last state of adja-cency is Full, which means that a complete database has been exchanged from the neighbor. On broadcast media, adjacencies are formed only with the DR and the BDR. All other neighbor goes up to the 2-way state. This is to reduce the number of adjacencies so that there will be less flooding traffic on the segment.

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Troubleshooting IP Routing Protocols
Troubleshooting IP Routing Protocols (CCIE Professional Development Series)
ISBN: 1587050196
EAN: 2147483647
Year: 2002
Pages: 260

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