Root: WRM Database > Information Technology > Certifications > CCNA > Acronyms > LSDB > What is OSPF?
Root: WRM Database > Information Technology > Certifications > CCNA > Acronyms > OSPF > What is OSPF?
Root: WRM Database > Information Technology > Certifications > CCNA > Acronyms > SPF > What is OSPF?
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Root: WRM Database > Information Technology > Certifications > CCNA > Routing Protocols > Link-State > OSPF > Adding Routes to IP Routing Table > What is OSPF?
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Root: WRM Database > Information Technology > Certifications > CCNA > Routing Protocols > Link-State > OSPF > LSDBs > What is OSPF?
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Root: WRM Database > Information Technology > Certifications > CCNA > Routing Protocols > Link-State > OSPF > Three Major Features > What is OSPF?
Root: WRM Database > Information Technology > Certifications > CCNA > Types of Routing Protocols > Link-State > Originally Developed > What is OSPF?



What is OSPF?


OSPF stands for Open Shortest Path First. OSPF is the most commonly used IP link-state routing protocol. Link-state routing protocols were originally developed mainly in the early to mid-1990s. The designers assumed that link speeds, router CPUs, and router memory would continue to improve over time, so the protocols were designed to provide much more powerful features by taking advantage of these improvements. By sending more information, and requiring the router to perform more processing, link-state protocols gain some important advantages over distance vector protocols - in particular much faster convergence. The goal remains the same - adding the currently best routes to the routing table - but these protocols use different methods to find and add those routes. The other link-state protocol for IP is Integrated IS-IS.




OSPF features can be broken into three major categories:
- neighbors
- database exchange
- route calculation


OSPF routers first form a neighbor relationship that provides a foundation for all continuing OSPF communications. After routers become neighbors, they exchange the contents of their respective LSDBs, through a process called database exchange. Finally, as soon as a router has a topology information in its link-state database (LSDB), it uses the Dijkstra Shortest Path First (SPF) algorithm to calculate the now-best routes and add those to the IP routing table.







References

Odom, Wendell (2008) CCNA ICND2 Official Exam Certification Guide, Second Edition. Indianapolis: Cisco Press.