Routing

Routing

RoutingWorking at a Small-to-Medium Business or ISP Chapter 6

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ObjectivesDescribe 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 ProtocolsRouting tables contain locally connected networks Routers use routing tables to determine routesRoutes can be statically assigned or dynamically learned through routing protocols

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Enabling Routing ProtocolsComponents of a route: destination value, subnet mask, gateway, route cost or metric

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Enabling Routing ProtocolsDirectly connected routesStatic routesDynamically updated routesDefault route

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Enabling Routing ProtocolsStatic routes are manually configuredStatic 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 tablesDistance metric can be based on hops, cost, bandwidth, speed, delay or reliabilityVector is the address of the next hop along a route

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Enabling Routing ProtocolsRouting Information Protocol (RIP):RFC 1058Distance vector using hop count metricUpdates every 30 seconds

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Enabling Routing ProtocolsEnhanced Interior Gateway Routing Protocol: (EIGRP)Enhanced distance vector protocolUses a variety of metricsCisco-proprietary

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Enabling Routing ProtocolsCharacteristics of link-state protocols:Full database of distant routers and interconnectionsLink-state advertisementsTopological databaseSPF algorithm

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Enabling Routing ProtocolsOpen Shortest Path First (OSPF):Non-proprietaryLink-stateRFC 2328Advanced protocol

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Enabling Routing ProtocolsCriteria for choosing routing protocols:Ease of managementEase of configurationEfficiency

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Enabling Routing ProtocolsDescribe and implement RIP routing on an integrated router

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Review of Routing Protocols# 2007 Cisco Systems, Inc. All rights reserved.Cisco Public16 2001, Cisco Systems, Inc. All rights reserved.

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Exterior Routing ProtocolsThe Internet is divided into autonomous systemsAS: a set of networks controlled by a single administration using the same internal routing policyEach ISP is an AS

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Exterior Routing ProtocolsInterior gateway protocols (IGPs) exchange routing information within an AS or individual organizationExterior gateway protocols (EGPs) exchange routing information between autonomous systems

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Exterior Routing ProtocolsEach AS uses dedicated border gateway routers to route packets across the Internet

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Exterior Routing ProtocolsISPs use exterior routing protocols to forward or control local and/or transit trafficExterior protocols enforce policies and support reliability

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Exterior Routing ProtocolsConfiguring Border Gateway Protocol (BGP):Configure the AS numberIdentify ISP neighbor router

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SummaryAll 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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