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Fundamentals of Networking Discovery 2, Chapter 6 Routing
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Objectives Describe the purpose and function of dynamic routing. Configure RIPv2 dynamic routing. Describe the use of exterior routing protocols across the Internet. Enable BGP on a customer router.
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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
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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
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The Routing Table
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Configuring the Static Route ip route destination_network subnet_mask next hop ip or outgoing int R1(config) #ip route 192.168.16.0 255.255.255.0 192.168.15.1 What would be the static route on R2 to reach the ladies’ network? PT 6.1.1.5
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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occur ▫ Bad cables, interfaces go down, better route learned ▫ Best route to a network in table ▫ Removes routes when no longer valid When all routers agree on topology= converged Two routers can exchange these tables as long as they use the same protocol
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Distance Vector Routing Passes updates every so often to connected neighbors Distance & Direction ▫ Metric (hops, speed, reliability, etc)
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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 0 away Star is 1 away Star is 2 away
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Practice 6.1.2.4 ▫ Activity for Routing Table 6.1.2.5 Lab ▫ Create a topology based on Routing Table
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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
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RIP RIPv1 ▫ Doesn’t send subnet mask in updates ▫ Classfull subnetting RIPv2 ▫ Classless subnetting
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RIP
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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
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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
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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
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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
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Which to Use??????
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DV vs. Link State
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Summary of Routing Protocols ProtocolDV or LSADMetricFeatures RIP v1DV120Hops 15 hops max RIP v2DV120Hops 15 max; VLSM EIGRP DV- Hybrid 90 Bandwidth, Load, Delay, Reliability Cisco’s; VLSM OSPFLS110Cost Multi- vendor; VLSM
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Routing May be multiple routes to same path ▫ Use AD (metrics) to pick best path ▫ Lowest AD is best
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Configure RIP Router(config)#router rip Router (config-router)#version 2 Router(config-router)#network network-number
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Verifying RIP Ping Show ip route Show ip protocols Debug ip rip PT 6.1.5.3 Lab 6.1.5.4
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Show ip protocols output
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Show ip route output Administrative Distance/metric; lower AD to a network=more trustworthy route
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Problems with RIP
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Autonomous Systems A set of networks under one administration ▫ An ISP & its customers ▫ Has one routing policy in the AS ▫ Each has unique AS# Large businesses register their own AS
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Activity
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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
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AS- LinkLink
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Routing Across Internet
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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
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ISP Handling of Traffic- LinkLink 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
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Configure the Border Gateway Static Route to ISP If router participates in the AS, configure BGP Lab 6.2.5 on PT
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Review- 13 Questions
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Fundamentals of Networking Discovery 2, Chapter 6 Routing
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