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Any Questions?. Chapter 8 Routing Protocol Theory. Dynamic Routing Protocol Overview Distance Vector Routing Protocol Features Link-State Routing Protocol Features. Do I know this?. Go through the Quiz- 5 minutes.

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  1. Any Questions?

  2. Chapter 8 Routing Protocol Theory • Dynamic Routing Protocol Overview • Distance Vector Routing Protocol Features • Link-State Routing Protocol Features

  3. Do I know this? Go through the Quiz- 5 minutes

  4. 1. Which of the following routing protocols are considered to use distance vector logic? a. RIP-1 b. RIP-2 c. EIGRP d. OSPF e. BGP f. Integrated IS-IS

  5. 1. Which of the following routing protocols are considered to use distance vector logic? a. RIP-1 b. RIP-2 c. EIGRP d. OSPF e. BGP f. Integrated IS-IS Answer: A&B

  6. 2. Which of the following routing protocols are considered to use link-state logic? a. RIP-1 b. RIP-2 c. EIGRP d. OSPF e. BGP f. Integrated IS-IS

  7. 2. Which of the following routing protocols are considered to use link-state logic? a. RIP-1 b. RIP-2 c. EIGRP d. OSPF e. BGP f. Integrated IS-IS Answer D&F

  8. 3. Which of the following routing protocols use a metric that is, by default, at least partially affected by link bandwidth? a. RIP-1 b. RIP-2 c. EIGRP d. OSPF e. BGP

  9. 3. Which of the following routing protocols use a metric that is, by default, at least partially affected by link bandwidth? a. RIP-1 b. RIP-2 c. EIGRP d. OSPF e. BGP Answer: C&D

  10. 4. Which of the following interior routing protocols support VLSM? a. RIP-1 b. RIP-2 c. EIGRP d. OSPF e. Integrated IS-IS

  11. 4. Which of the following interior routing protocols support VLSM? a. RIP-1 b. RIP-2 c. EIGRP d. OSPF e. Integrated IS-IS Answer: B, C, D&E

  12. 5. Which of the following situations would cause a router using RIP-2 to remove all the routes learned from a particular neighboring router? a. RIP keepalive failure b. No longer receiving updates from that neighbor c. Updates received 5 or more seconds after the last update was sent to that neighbor d. Updates from that neighbor have the global “route bad” flag

  13. 5. Which of the following situations would cause a router using RIP-2 to remove all the routes learned from a particular neighboring router? a. RIP keepalive failure b. No longer receiving updates from that neighbor c. Updates received 5 or more seconds after the last update was sent to that neighbor d. Updates from that neighbor have the global “route bad” flag Answer: B

  14. 6. Which of the following distance vector features prevents routing loops by causing the routing protocol to advertise only a subset of known routes, as opposed to the full routing table, under normal stable conditions? a. Counting to infinity b. Poison reverse c. Holddown d. Split horizon e. Route poisoning

  15. 6. Which of the following distance vector features prevents routing loops by causing the routing protocol to advertise only a subset of known routes, as opposed to the full routing table, under normal stable conditions? a. Counting to infinity b. Poison reverse c. Holddown d. Split horizon e. Route poisoning Answer: D

  16. 7. Which of the following distance vector features prevents routing loops by advertising an infinite metric route when a route fails? a. Holddown b. Full updates c. Split horizon d. Route poisoning

  17. 7. Which of the following distance vector features prevents routing loops by advertising an infinite metric route when a route fails? a. Holddown b. Full updates c. Split horizon d. Route poisoning Answer: D

  18. 8. A router that is using a distance vector protocol just received a routing update that lists a route as having an infinite metric. The previous routing update from that neighbor listed a valid metric. Which of the following is not a normal reaction to this scenario? a. Immediately send a partial update that includes a poison route for the failed route b. Put the route into holddown state c. Suspend split horizon for that route and send a poison reverse route d. Send a full update listing a poison route for the failed route

  19. 8. A router that is using a distance vector protocol just received a routing update that lists a route as having an infinite metric. The previous routing update from that neighbor listed a valid metric. Which of the following is not a normal reaction to this scenario? a. Immediately send a partial update that includes a poison route for the failed route b. Put the route into holddown state c. Suspend split horizon for that route and send a poison reverse route d. Send a full update listing a poison route for the failed route Answer: A

  20. 9. An internetwork is using a link-state routing protocol. The routers have flooded all LSAs, and the network is stable. Which of the following describes what the routers will do to reflood the LSAs? a. Each router refloods each LSA using a periodic timer that has a time similar to distance vector update timers. b. Each router refloods each LSA using a periodic timer that is much longer than distance vector update timers. c. The routers never reflood the LSAs as long as the LSAs do not change. d. The routers reflood all LSAs whenever one LSA changes.

  21. 9. An internetwork is using a link-state routing protocol. The routers have flooded all LSAs, and the network is stable. Which of the following describes what the routers will do to reflood the LSAs? a. Each router refloods each LSA using a periodic timer that has a time similar to distance vector update timers. b. Each router refloods each LSA using a periodic timer that is much longer than distance vector update timers. c. The routers never reflood the LSAs as long as the LSAs do not change. d. The routers reflood all LSAs whenever one LSA changes. Answer: B

  22. 10. Which of the following is true about how a router using a link-state routing protocol chooses the best route to reach a subnet? a. The router finds the best route in the link-state database. b. The router calculates the best route by running the SPF algorithm against the information in the link-state database. c. The router compares the metrics listed for that subnet in the updates received from each neighbor and picks the best (lowest) metric route.

  23. 10. Which of the following is true about how a router using a link-state routing protocol chooses the best route to reach a subnet? a. The router finds the best route in the link-state database. b. The router calculates the best route by running the SPF algorithm against the information in the link-state database. c. The router compares the metrics listed for that subnet in the updates received from each neighbor and picks the best (lowest) metric route. Answer: B

  24. Any Questions?

  25. Dynamic Routing Protocols • Routing protocol: A set of messages, rules, and algorithms used by routers for the overall purpose of learning routes. This process includes the exchange and analysis of routing information. Each router chooses the best route to each subnet (path selection) and finally places those best routes in its IP routing table. Examples include RIP, EIGRP, OSPF, and BGP. • Routed protocol and routable protocol: Both terms refer to a protocol that defines a packet structure and logical addressing, allowing routers to forward or route the packets. Routers forward, or route, packets defined by routed and routable protocols. Examples include IP and IPX (a part of the Novell NetWare protocol model). Pg 309

  26. Routing Protocol Functions • Routers need routing protocols to fill the routing table with destinations • If no matching destination for a packet, router will drop it Pg 310

  27. Routing Protocols 1. Learn routing information about IP subnets from other neighboring routers. 2. Advertise routing information about IP subnets to other neighboring routers. 3. If more than one possible route exists to reach one subnet, pick the best route based on a metric. 4. If the network topology changes—for example, a link fails—react by advertising that some routes have failed, and pick a new currently best route. (This process is called convergence.) Pg 310

  28. Routing Functions in action • Function 1 • Both R1 and R3 learn about a route to subnet 172.16.3.0/24 from R2 (function 1). • Function 2 • After R3 learns about the route to 172.16.3.0/24 from R2, R3 advertises that route to R1. R1 must make a decision about the two routes it learned about for reaching subnet 172.16.3.0/24: one with metric 1 from R2, and one with metric 2 from R3. • Function 3 • R1 chooses the lower metric route through R2 Pg 310-311

  29. Interior vs. exterior • IGP: A routing protocol that was designed and intended for use inside a single autonomous system (AS) • EGP: A routing protocol that was designed and intended for use between different autonomous systems Pg 311

  30. Autonomous Systems • An AS is an internetwork under the administrative control of a single organization. • An internetwork created and paid for by a single company is probably a single AS, • An internetwork created by a single school system is probably a single AS. • Large divisions of a state or national government, • Each ISP is also typically a single different AS. • Some routing protocols work best inside a single AS • These routing protocols are called IGPs. • Routing protocols designed to exchange routes between routers in different autonomous systems are called EGPs. • Currently, only one legitimate EGP exists: the Border Gateway Protocol [BGP] Pg 312

  31. EGP, IGP and AS Pg 312

  32. Any Questions?

  33. IGP Algorithms • Distance vector (sometimes called Bellman-Ford after its creators) • Link-state • Balanced hybrid (sometimes called enhanced distance vector) Pg 313

  34. Brief History • Distance Vectors first • RIP then Cisco’s IGRP • Links States solved some of the Distance Vector Problems • Slow convergence • Routing loops • Link States require more planning • OSPF • IS-IS • Hybrid • EIGRP Pg 313

  35. Routing Metrics Pg 314

  36. Metrics Compared Pg 314

  37. Metrics Compared Pg 314

  38. IGP Comparisons Pg 315

  39. IGP Features Pg 316

  40. Any Questions?

  41. Administrative Distance • Measures the quality of the routing information • The “better” the information, the lower the AD • If more than one protocol is in use, the AD determines which routes will be used Pg 316

  42. AD Pg 317

  43. ADs • Admin distance can also be controlled manually • ip route 10.1.3.0 255.255.255.0 10.1.130.253 210 • The 210 is the Admin Distance Pg 317

  44. Any Questions?

  45. Distance Vector Protocols • Distance Vector describes what the router knows about the route to the destination • Distance-How many hops • Vector-Which direction to go Pg 318

  46. Distance Vector Protocols • Send full routing table periodically • Sends the destinations it knows • Sends the metric • Figure 8-6-R2 tells R1 that 172.30.21.0 is 1 hop • Routers that receive updates will add routes to their tables • The next hop will be the interface through which they received the update Pg 319

  47. Distance Vector Functioning • Periodic: The hourglass icons represent the fact that the updates repeat on a regular cycle. RIP uses a 30-second update interval by default. • Full updates: The routers send full updates every time instead of just sending new or changed routing information. • Full updates limited by split-horizon rules: The routing protocol omits some routes from the periodic full updates because of split-horizon rules. Split horizon is a loopavoidance feature that is covered in the next few pages. Pg 320

  48. Routing Loops • Since we are routing based on other routers info, and we send our full table, sometimes we get loops • How do we prevent loops • Route Poisoning • Split Horizon • Poison Reverse and Triggered Updates • Hop Count Limit Pg 320

  49. Route Poisoning • If a route fails, loops can happen until everyone knows • Route poisoning marks route as unreachable • Sets hop count to infinity Pg 321

  50. Route Poisoning 1. R2’s Fa0/1 interface fails. 2. R2 removes its connected route for 172.30.22.0/24 from its routing table. 3. R2 advertises 172.30.22.0 with an infinite metric, which for RIP is metric 16. 4. R1 keeps the route in its routing table, with an infinite metric, until it removes the route from the routing table. Pg 321

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