© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.1

Routing

Working at a Small-to-Medium Business or ISP – Chapter 6

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Objectives Describe the purpose and function of dynamic routing

and the protocols used to implement it.

Configure RIPv2 dynamic routing using the Cisco IOS.

Describe the use of exterior routing protocols across the Internet.

Enable BGP on a customer site router.

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Enabling Routing Protocols Routing tables contain locally connected

networks

Routers use routing tables to determine routes

Routes can be statically assigned or dynamically learned through routing protocols

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Enabling Routing Protocols Components of a route: destination value,

subnet mask, gateway, route cost or metric

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Enabling Routing Protocols Directly connected routes

Static routes

Dynamically updated routes

Default route

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Enabling Routing Protocols Static routes are manually configured

Static routes are suitable for small networks with few changes

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Enabling Routing ProtocolsCharacteristics of distance vector protocols:

Routers share copies of routing tables

Distance metric can be based on hops, cost, bandwidth, speed, delay or reliability

Vector is the address of the next hop along a route

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Enabling Routing ProtocolsRouting Information Protocol (RIP):

RFC 1058

Distance vector using hop count metric

Updates every 30 seconds

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Enabling Routing ProtocolsEnhanced Interior Gateway Routing Protocol:

(EIGRP)

Enhanced distance vector protocol

Uses a variety of metrics

Cisco-proprietary

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Enabling Routing ProtocolsCharacteristics of link-state protocols:

Full database of distant routers and interconnections

Link-state advertisements

Topological database

SPF algorithm

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Enabling Routing ProtocolsOpen Shortest Path First (OSPF):

Non-proprietary

Link-state

RFC 2328

Advanced protocol

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Enabling Routing ProtocolsCriteria for choosing routing protocols:

Ease of management

Ease of configuration

Efficiency

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Enabling Routing Protocols Describe and implement RIP routing on an

integrated router

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Exterior Routing Protocols The Internet is divided into autonomous

systems

AS: a set of networks controlled by a single administration using the same internal routing policy

Each ISP is an AS

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Exterior Routing Protocols Interior gateway protocols (IGPs) exchange

routing information within an AS or individual organization

Exterior gateway protocols (EGPs) exchange routing information between autonomous systems

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Exterior Routing Protocols Each AS uses dedicated border gateway

routers to route packets across the Internet

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Exterior Routing Protocols ISPs use exterior routing protocols to forward

or control local and/or transit traffic

Exterior protocols enforce policies and support reliability

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Exterior Routing ProtocolsConfiguring Border Gateway Protocol (BGP):

Configure the AS number

Identify ISP neighbor router

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Summary All routers make routing decisions by looking up information stored

in their routing tables.

Routes can be statically assigned by an administrator, or dynamically learned by the router via a routing protocol.

Routing protocols use either distance-vector or link-state algorithms to calculate the best routes to each destination.

Criteria such as ease of management, ease of configuration, and efficiency must be considered when selecting a routing protocol for use within an organization.

Organizations are also called Autonomous Systems.

Between Autonomous Systems, Exterior Gateway routing protocols control the flow of traffic.

ISPs handle Internet traffic through the use of routing policies.

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