1. Lecture #3 OSPF Asst.Prof. Dr.Anan Phonphoem Department of Computer Engineering, Faculty of Engineering, Kasetsart University, Bangkok, Thailand

2. Outline Distance VS. Link-State Route selection Link-State network (OSPF) Link-State Operation Basic OSPF configuration and verification

3. Distance Vector VS. Link-State

4. Pro/Con of Link-State

5. Route Selection RIP OSPF

6. Multiple-Area OSPF Network Single-Area

7. Terminology Link Link-State Link-State db Area Cost Routing Table Adjacency db DR / BDR

8. OSPF path cost Cisco Default Value

9. OSPF Packet Header

10. Concept of link state routing

11. Cost (weight) in link state routing Cost is applied only by router Cost is applied when packet leaves the router

12. Link state packet Cost: weight (traffic, security level, link state)

13. Flooding of A’s LSP

14. Link state database

15. Shortest path tree Build the tree, start by identifying a root  attach all reached nodes Compare arcs and find the lowest cost  add this node (to be permanent) and its arcs (temp) Examine database and identify the reachable node Repeat the last two steps

16. Costs in the Dijkstra algorithm

17. Shortest path calculation Step1 Step2

18. Shortest path calculation Step3 Step4

19. Shortest path calculation Step5 Step6

20. Shortest path calculation – S7

21. Shortest path calculation – S8

22. Shortest path calculation – S9

23. Shortest path calculation – S10

24. Shortest path calculation – S11

25. Shortest path calculation – S12

26. Shortest path calculation – S13

27. Link state routing table for router A

28. Basic configuration Wildcard-Mask Area ID

29. Basic configuration - Loopback Setup Loopback Ensure that at least one is active (For stability)

30. Basic configuration - priority Setup priority For DR/BDR selection

31. OSPF verification show ip protocolshow ip route show ip ospfshow ip ospf interface show ip ospf database show ip ospf neighbor detail clear ip route *clear ip route a.b.c.d debug ip ospf eventsdebug ip ospf adj