Routing Protocols

1. Chapter 14 Routing Protocols RIP, OSPF, BGP

2. Figure 14-1 Autonomous systems

3. Figure 14-2 Popular routing protocols Link State Distance Vector Path Vector

4. Distance Vector Routing. Forouzan + CCNA: • Slow convergence. • Routing loops. • Counting to infinity. • Split horizon • Route poisoning. • Triggered update.

5. 14.3 RIP: Routing Information Protocol Exposición equipo 5

6. Example of updating a routing

7. Initial routing tables in a small autonomous system

8. Final routing tables for the previous figure

9. RIP message format

10. Request messages

11. Example 1 What is the periodic response sent by router R1 in Figure 13.8 (next slide)? Assume R1 knows about the whole autonomous system.

12. Example 1

13. Solution R1 can advertise three networks 144.2.7.0, 144.2.9.0, and 144.2.12.0. The periodic response (update packet) is shown in Figure 13.9 (next slide).

14. Solution to Example 1

15. RIP timers

16. Example 2 A routing table has 20 entries. It does not receive information about five routes for 200 seconds. How many timers are running at this time?

17. Solution The timers are listed below: Periodic timer: 1 Expiration timer: 20 - 5 = 15 Garbage collection timer: 5

18. Slow convergence

19. Hop count

20. Instability

21. Split horizon

22. Poison reverse

23. RIP-v2 Format

24. RIP version 2 supports CIDR.

25. Authentication

26. RIP uses the services of UDP on well-known port 520.

27. 14.5 OSPF: Open Shortest Path First

28. Areas in an autonomous system

29. Types of links

30. Point-to-point link

31. Transient link

32. Stub link

33. Example of an internet

34. Graphical representation of an internet

35. Types of LSAs

36. Router link

37. Network link

38. Summary link to network

39. Summary link to AS boundary router

40. External link

41. Example 3 In Figure 14.31 (next slide), which router(s) sends out router link LSAs?

42. Figure 14-31 Example 3 and Example 4

43. Solution All routers advertise router link LSAs. R1 has two links, Net1 and Net2. R2 has one link, Net2 in this AS. R3 has two links, Net2 and Net3.

44. Example 4 In Figure 14.31, which router(s) sends out the network link LSAs?

45. Solution All three network must advertise network links: Advertisement for Net1 is done by R1 because it is the only router and therefore the designated router. Advertisement for Net2 can be done by either R1, R2, or R3, depending on which one is chosen as the designated router. Advertisement for Net3 is done by R3 because it is the only router and therefore the designated router.

46. In OSPF, all routers have the same link state database.

47. Shortest path calculation Dijkstra algorithm Start Set root to local node and move it to tentative list Tentative list is empty? Yes No Among nodes in tentative list, move the one with the shortest path to permanent list. Add each unprocessed neighbor of last moved node to tentative list if not already There. If neighbor is in the tentative list with larger cumulative cost, replace with new one. Stop

48. Shortest path calculation Dijkstra algorithm

49. 0 F

50. 0 F 5 9 N5 N3