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OSPF
OSPF is an interior gateway protocol that uses link state routing and the Shortest Path First algorithm to calculate the best routes between destinations in a router network. It elects a Designated Router and Backup Designated Router on each multi-access network that distribute routing information to other routers through link state advertisements. OSPF supports authentication, manual route summarization, and metric adjustments to optimize routing behavior.
OSPF
- 1.
- 2. Guide Line (Part1) OSPF Review Link state concept OSPF Feature Summary OSPF Terminology OSPF Configuration OSPF Verification OSPF neighboring over LAN
- 3. Link state concept Neighbor Discovery Exchange information Calculate best path
- 4. OSPF Feature Summary FeatureDescription Transport IP protocol type 89(doesn’t use UDP or TCP( Metric Based on cumulative cost of all outgoing interface in a router Hello interval Sent hello message all 10 sec Dead interval Down neighbor if it doesn’t receive replay from neighbor after 40 sec Update destination address Normally sent 224.0.0.5(All SPF Routers)and 224.0.0.6(All designated Routers( Full or partial update Full update are used when new neighbors are discovered; otherwise partial updated are used. Authentication Support MD5 and clear text authentication Router tag Allow OSPF to tag routers as they are redistributed in to OSPF Manual router summarization Allow route summarization at ARB routers only
- 5. OSPF Terminology Shortestpath First(SPF) Link state database(LSDB) Link state update(LSU) Link state advertisement(LSA) Area Area Border Router(ABR) Backbone Router Designated Router(DR) Backup Designated Router(BDR)
- 6. OSPF Configuration Rtr(config)# routerospf process-id Rtr(config-router)#network address wildcard-mask area area-id
- 7. Optional Commands: Rtr(config-router)# default-informationoriginate (Send default) Rtr(config-router)# area area authentication (Plain authen.) Rtr(config-router)# area area authentication message-digest(md5 authen.) Rtr(config)# interface loopback number (Configure lo as RtrID) Rtr(config-if)# ip ospf priority <0-255> (DR/BDR election) Rtr(config-if)# bandwidth kbps (Modify default bandwdth) RTB(config-if)# ip ospf cost cost (Modify inter. cost) Rtr(config-if)# ip ospf hello-interval seconds (Modify Hello) Rtr(config-if)# ip ospf dead-interval seconds (Modify Dead) Rtr(config-if)# ip ospf authentication-key passwd (Plain/md5authen) Rtr(config-if)# ip ospf message-digest-key key-id md5 password
- 8. OSPF Verification Showip protocol Show ip ospf neighbor Show ip ospf brief Show ip ospf database Show ip route
- 9. OSPF neighboring overLAN Enabling OSPF by Network Command or per interface Network command IP OSPF interface sub command Passive interface Setting must match for OSPF neighbor
- 10. Guide Line (Part2) Optimizing Convergence Using a unique Router ID Using Same MTU OSPF Authentication