Fundamentals of NetworkingDiscovery 2, Chapter 6Routing

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.

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▫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

The Routing Table

Static Routes

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

Dynamic Routes

Distance Vector

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changes occur▫Bad cables, interfaces go down, better route learned▫Best route to a network in table▫Removes routes when no longer valid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

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

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

Star is 2 away

Practice•6.1.2.4▫Activity for Routing Table

•6.1.2.5 Lab▫Create a topology based on Routing Table

RIP:Distance Vector

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

RIP•RIPv1▫Doesn’t send subnet mask in updates▫Classfull subnetting

•RIPv2▫Classless subnetting

RIP

EIGRP:Distance Vector

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

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

Dynamic RoutesLink State

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

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

Which to Use??????

DV vs. Link State

Summary of Routing Protocols

Protocol DV or LS AD Metric Features

RIP v1 DV 120 Hops 15 hops max

RIP v2 DV 120 Hops15 max;VLSM

EIGRP DV-Hybrid 90

Bandwidth, Load, Delay, Reliability

Cisco’s;VLSM

OSPF LS 110 CostMulti-vendor;VLSM

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

Configuring RIP

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

Verifying RIP• Ping• Show ip route• Show ip protocols• Debug ip rip

• PT 6.1.5.3

• Lab 6.1.5.4

Show ip protocols output

Show ip route output

Administrative Distance/metric; lower AD to a network=more trustworthy route

Problems with RIP

Exterior Routing Protocols

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

Activity

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

AS- Link

Routing Across Internet

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

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

Configure the Border Gateway

•Static Route to ISP• If router participates in the AS, configure BGP

Lab 6.2.5 on PT

Review- 13 Questions

Fundamentals of NetworkingDiscovery 2, Chapter 6Routing