OSPF Theory

 

1. OSPF stand for Open Shortest Path First.
2. Standard Protcoocl
3. It's Link State Protocol
4. It use Shortest Path First of Dijkistra Algorithm.
5. Unlimited Hop Count support.
6. Metric is cost.
7. Administrative distance is 110.
8. It's a classless routin protocol.
9. OSPF always send the hello packets in every 10 seconds.
10. Hold down timer is 40 second. It terminate the link if did not share the hello packet till 40 second.
11. Multicast address is 224.0.0.5
12. It support equal cost load balancing.

Router ID:- The highest IP address of active physical interface of the router is Router ID.

If logical interface is configured, the highest IP address of the logical interface is Router ID.

Loopback always beat the physical interface.

Router Types:-

In OSPF depending upon the network design and configuration we have different types of routers.

Internal Routers are routers whose interfaces all belong to the same area. These routers have a sigle Link STate Database.

Area Border Routers(ABR) It connects one or more areas to the backbone area and has at least one interface that belongs to the backbone,Backbone Router Area 0 routers.

Autonomous System Boundary Router(ASBR) router participating in OSPF and other protocol like RIP,EIGRP and BGP.

OSPF Maintains Three Table:

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Neighbor Table: Neighbor table contains information about the directly connected OSPF neighbors forming adjacency.

Database Table: Database table contains information aabout the entire view of the topology with respect to each router.

Routing INformation Table: Routing table contain information about the best path calculated by the shortest path first algorithm in the database table.