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CCNP Routing and Switching Quick Reference Library: ROUTE 300-101, SWITCH 300-115, and TSHOOT 300-135 Quick References by Brent Stewart, Denise Donohue

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Chapter 5. OSPF

OSPF Overview

Open Shortest Path First (OSPF) is an open-standard link-state routing protocol that uses the Shortest Path First (SPF) algorithm to determine its best path to each network. OSPFv2 supports IPv4 routing and OSPFv3 supports both IPv4 and IPv6 routing.

Link-state routers create a database that reflects the structure of their area in the network. Link-state routing protocols learn more information on the structure of the network than other routing protocols and thus can make more informed routing decisions.

OSPF routers exchange hellos with each neighbor, learning router ID (RID) and cost. Neighbor information is kept in the Adjacency database. The router then constructs the appropriate link-state advertisements (LSA), ...

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