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CCNP Quick Reference Sheets Bundle: Exams 642-901, 642-812, 642-845, 642-825 by Jay Swan, Denise Donohue, Brent Stewart

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Chapter 3. OSPF

OSPF Overview

OSPF is an open-standard, classless routing protocol that converges quickly and uses cost as a metric (Cisco IOS automatically associates cost with bandwidth).

OSPF is a link-state routing protocol and uses Dijkstra’s Shortest Path First (SPF) algorithm to determine its best path to each network. The first responsibility of a link-state router is to create a database that reflects the structure of the network. Link state routing protocols learn more information on the structure of the network than other routing protocols, and thus are able to 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. ...

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