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6: Routing

6: Routing. Working at a Small to Medium Business. Basics. Routers can be used to break network smaller Subnet To go from router to router Routing table Finds route to other networks Statically set Dynamically learned. The Routing Table. Router looks at destination IP & SM

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6: Routing

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  1. 6: Routing Working at a Small to Medium Business

  2. Basics • Routers can be used to break network smaller • Subnet • To go from router to router • Routing table • Finds route to other networks • Statically set • Dynamically learned

  3. The Routing Table • Router looks at destination IP & SM • ANDing the destination IP & SM • Result is a network # • Looks in table for the match & forwards it out that interface • No match= default route, if set • Routing Table has list of networks & paths

  4. The Routing Table

  5. Static Routes

  6. Configuring the Static Route • ip route destination_networksubnet_masknext hop ip or outgoing int • R1(config) #ip route 192.168.16.0255.255.255.0192.168.15.1 What would be the static route on R2 to reach the ladies’ network? PT 6.1.1.5

  7. Dynamic Routes Distance Vector

  8. Dynamic Routing Protocols • Maintain tables when changes occur • Bad cables, interfaces go down, better route learned • Best route to a network in table • Removes routes when no longer valid • When all routers agree on topology= converged • Two routers can exchange these tables as long as they use the same protocol

  9. Distance Vector Routing • Passes updates every so often to connected neighbors • Distance & Direction • Metric (hops, speed, reliability, etc)

  10. Distance Vector Routing & Lab • Interface that leads to the connected network has a distance (metric) of 0 • Neighbors update each other & add on how far away it is Star is 2 away Star is 1 away Star is 2 away Star is 0 away

  11. Practice • 6.1.2.4 • 6.1.2.5 Lab

  12. RIP: Distance Vector

  13. RIP- Routing Information Protocol • DV • Metric is Hops • Only15 Max; 16 is unreachable (D) • Updates every 30 seconds by default • Sends entire routing table (D) • If change, update sent immediately (triggered) • Slow to converge whole network (D) • Administrative Distance is 120

  14. RIP • RIPv1 • Doesn’t send subnet mask in updates • Classfull subnetting • RIPv2 • Classless subnetting

  15. RIP

  16. EIGRP: Distance Vector

  17. EIGRP • Enhanced Interior Gateway Routing Protocol • Cisco proprietary DV (mix LS & DV) • AD of 90 • Many metrics (bandwidth, delay, load, reliability) • Up to 224 hops • Routing Table, Neighbor Table, Topology Table • Updates on start of router & only when a change happens • VLSM Support

  18. EIGRP Tables • Neighbor Table • Has info about neighbor direct connect routers • Topology Table • Built from advertisements of its neighbors • Contains ALL routes advertised by neighbor routers • DUAL calculates the shortest path to a destination and installs it into the routing table • Is able to find the best alternate path quickly when a network change occurs • If no alternate route exists it asks its neighbors to find a new path to the destination

  19. Dynamic Routes Link State

  20. Link State Routing • Knows routes further away • LSA • Topological database • Info from LSAs • SPF • Each change causes new calc & database update • Map of network from point of view of the router • Info in tree is used to build the routing table

  21. OSPF • AD of 110 • Metric is cost • Uses SPF • Sends updates only when the topology changes • Does not send periodic updates of the entire routing table • Fast convergence • Supports VLSM • Provides route authentication

  22. Which to Use??????

  23. DV vs. Link State

  24. Summary of Routing Protocols

  25. Routing • May be multiple routes to same path • Use AD (metrics) to pick best path • Lowest AD is best

  26. Configuring RIP

  27. Configure RIP • Router(config)#router rip • Router (config-router)#version 2 • Router(config-router)#network network-number

  28. Verifying RIP • Ping • Show ip route • Show ip protocols • PT 6.1.5.3 • Lab 6.1.5.4

  29. Show ip protocols output

  30. Show ip route output Administrative Distance/metric; lower AD to a network=more trustworthy route

  31. Problems with RIP

  32. Exterior Routing Protocols

  33. Autonomous Systems • A network under one administration • An ISP & its customers • Large businesses have their own AS • Each has unique AS# • Manages all routes to it

  34. Activity

  35. Routing Between AS • IGP runs within your network & between your routers • RIP, EIGRP, OSPF • EGP runs between different AS • Most common is BGP • Runs on border gateway routers • The router at the end of an AS • Finds the best path between AS

  36. AS- Link

  37. Routing Across Internet

  38. Help from the ISP • Keep the Internet connection available • ISP provides backup routes & routers • ISP advertises routes to other AS • If route fails, sends an update with a backup route

  39. ISP Handling of Traffic- Link • Local traffic • Stays within the AS • Transit traffic • Outside of AS to go in/through AS • Like detouring traffic from Rt.55 onto Tanyard Rd. • Could cause overflow of traffic • Can’t handle that much • AS may or may not allow this traffic

  40. Configure the Border Gateway • Static Route to ISP • If router participates in the AS, configure BGP Lab 6.2.5 on PT

  41. Review

  42. 6: Routing Working at a Small to Medium Business

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