1. --- CCIE R&S Advanced Lab --- --- Session 4 OSPF ---

2. Copyright© Network Learning Inc. 2008 2 Topics Covered OSPF Network Types Adjacencies Area types Authentication Summaries Filtering New Features

3. Copyright© Network Learning Inc. 2008 3 OSPF Know where OSPF is on the DOC CD. How can OSPF be manipulated ? Check the show IP protocols command

4. Copyright© Network Learning Inc. 2008 4 Network Types The easiest configuration is to configure all OSPF frame relay interfaces for point-to-multipoint If the lab prohibits you from changing the network type configure NBMA Frame Relay InterfaceOSPF Network Type PhysicalNon-Broadcast Multipoint SubPoint-to-Multipoint Point-to-Point SubPoint-to-Point

5. Copyright© Network Learning Inc. 2008 5 Hello and Dead Timers In order to form neighbor adjacency, hello and dead timers must match Timer differ based on network type configuration broadcast: Hello time (10 seconds), dead time (40 seconds) point-to-point:Hello time (10 seconds), dead time(40 seconds) non-broadcast:Hello Time (30 seconds), dead time (120 seconds) Timers can be manually adjusted through the “ip ospf hello-interval” and “ip ospf dead-interval” interface commands

6. Copyright© Network Learning Inc. 2008 6 Miscellaneous OSPF - Timers Basic Timers Hello-interval –ip ospf hello-interval 20 – automatically changes the dead-interval to 80, dead = hello x 4 Dead-interval –ip ospf dead-interval 50 – does NOT change the hello-interval

7. Copyright© Network Learning Inc. 2008 7 OSPF Timers – Fast Hellos Added in 12.2T15 Enables faster convergence Sets Dead timer to 1 second, hello timer based on hello-multiplier. Example – set hello to 250ms ip ospf dead-interval minimal hello-multiplier 4

8. Copyright© Network Learning Inc. 2008 8 Neighbor Adjacency issues Mismatched hello Authentication Area ID doesn’t match Area Stub flag doesn’t match Duplicate Router ID

9. Copyright© Network Learning Inc. 2008 9 Area Type All routers in an OSPF area must have the same area type set Totally Stubby and Totally NSSA have the ‘no-summary’ command added to the ABR NSSA does not inject a default route automatically. Must be manually configured on the ABR: area 2 nssa default-information-originate

10. Copyright© Network Learning Inc. 2008 10 OSPF Authentication Uses either Clear Text or MD5 Can do either Area Authentication or Link Authentication If area 0 has authentication, any virtual links must have the same authentication configured Watch for extra spaces on your passwords

11. Copyright© Network Learning Inc. 2008 11 Area Authentication Clear Text R1(config)# router ospf 1 R1(config-router)# area 0 authentication R1(config)# int serial 0 R1(config-if)# ip ospf authentication-key cisco MD5 R1(config)# router ospf 1 R1(config-router)# area 0 authentication message-digest R1(config)# int s0 R1(config-if)# ip ospf message-digest-key 1 md5 cisco

12. Copyright© Network Learning Inc. 2008 12 Link Authentication Clear Text R1(config-if)# int s0 R1(config-if)# ip ospf authentication R1(config-if)# ip ospf authentication-key cisco MD5 R1(config-if)# int s0 R1(config-if)# ip ospf authentication message-digest R1(config-if)# ip ospf message-digest-key 1 md5 cisco

13. Copyright© Network Learning Inc. 2008 13 Virtual Link Authentication Clear Text R1(config)# router ospf 1 R1(config-router)# area 1 virtual-link 2.2.2.2 authentication-key cisco MD5 R1(config)# router ospf 1 R1(config-router)# area 1 virtual-link 2.2.2.2 message-digest-key 1 md5 cisco If you are required to traverse a VL you must negate capability transit.

14. Copyright© Network Learning Inc. 2008 14 Connecting a Non-Backbone Area Through a Stub Area Generic Routing Encapsulation (GRE) allows you to connect a discontiguous area to the backbone through a stub area GRE will cause extra packet overhead due to tunnel header information

15. Copyright© Network Learning Inc. 2008 15 OSPF New Features Max LSA

16. Copyright© Network Learning Inc. 2008 16 OSPF New Features Cont. Maximum Prefixes (Networks)

17. Copyright© Network Learning Inc. 2008 17 OSPF New Features Cont. Prevent OSPF router from being transit Max Metric uses 65535 (16 bits)

18. Copyright© Network Learning Inc. 2008 18 OSPF Summarization Two ways to summarize Area range used to summarize between OSPF areas. Always done on an ABR –area 2 range 100.5.50.0 255.255.255.0 Summary-address used to summarize external routes redistributed into OSPF. Always done on an ASBR –summary-address 100.5.50.0 255.255.255.0 Will inject a NULL0 route into the routing table. MUST get rid of the NULL0 –no discard-route internal – used with area range –no discard-route external – used with summary-address

19. Copyright© Network Learning Inc. 2008 19 Filtering in OSPF Distribute list only inbound and will not affect LSAs

20. Copyright© Network Learning Inc. 2008 20 Break Area 0 R1 and R2 have full knowledge of Area 0 routes and R3 and R4 have no knowledge.

21. Copyright© Network Learning Inc. 2008 21 Prevent type 7 to 5 routes from Area 0 Area 5 NSSA

22. Copyright© Network Learning Inc. 2008 22 SUPER LAB 1