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OSPF

OSPF. Open Shortest Path First ( OSPF ) is a link-state routing protocol for Internet Protocol ( IP ) networks. It uses a link state routing algorithm and falls into the group of interior routing protocols (also referred to as IGP ), operating within a single autonomous system ( AS ).

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OSPF

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  1. OSPF Open Shortest Path First (OSPF) is a link-state routing protocol for Internet Protocol (IP) networks. It uses a link state routing algorithm and falls into the group of interior routing protocols (also referred to as IGP), operating within a single autonomous system (AS).

  2. Areas • Backbone area (area 0) • Stub area • Not-so-stubby area (NSSA) Mfawa Alfred Onen - 2013

  3. Router ID Router ID is going to be chosen automatically unless configured manually, using the 'router-id A.B.C.D' command in OSPF configuration context. Initially, a router tries to choose its ID based on the following order of operation: • Router chooses numerically the highest IP addressoff of the loopback interface. • In case there is no loopback interface configured, the router is going to choose numerically the highest IP address off of the physical interface. Mfawa Alfred Onen - 2013

  4. Link State Advertisement (LSA) OSPF routers exchange LSAs by flooding them to all OSPF neighbors. This flooding results in creating the same Link-State Database (LSDB) on all routers in the area. LSDB is a topology database, (kind of a "road map"), shared by all routers in the area. Then, each router runs Dijkstra's SPF algorithm to choose the best path to each destination, placing itself as the root (starting point). The product of SPF algorithm operation is the routing table. Mfawa Alfred Onen - 2013

  5. Designated Router (DR) A designated router (DR) is the router interface elected among all routers on a particular multi-access network segment, generally assumed to be a broadcast multi-access network. Mfawa Alfred Onen - 2013

  6. Backup Designated Router (BDR) A backup designated router (BDR) is a router that becomes the designated router if the current designated router has a problem or fails. The BDR is the OSPF router with second highest priority at the time of the last election. Mfawa Alfred Onen - 2013

  7. Useful OSPF Commands (Cisco IOS) Mfawa Alfred Onen - 2013

  8. Useful OSPF Commands (Cisco IOS) CONTD. Mfawa Alfred Onen - 2013

  9. Enough with the Boring Stuff, Show us a DEMO!! Mfawa Alfred Onen - 2013

  10. Hands On Lab – Setup OSPF on All R1,2 and 3 Mfawa Alfred Onen - 2013

  11. That’s it? nw it makes more sense. Mfawa Alfred Onen - 2013

  12. Further Reading • http://computernetworkingnotes.com/routing-static-dynamics-rip-ospf-igrp-eigrp/ospf-routing-configurations.html • http://ciscoiseasy.blogspot.com/2011/02/lesson-40-ospf-fundamentals-part3.html • http://en.wikipedia.org/wiki/Open_Shortest_Path_First Mfawa Alfred Onen - 2013

  13. Questions? Mfawa Alfred Onen - 2013

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