Controlling Route Distribution and Reception 383preferred-value preferred-value in Routing Policy Commands of the IPRouting Volume.Controlling RouteDistribution andReceptionPrerequisites Before configuring this task, you have completed BGP basic configuration.Configuring BGP RouteRedistributionBGP can advertise the routing information of the local AS to peering ASs, but itredistributes routing information from IGP into BGP rather than self-finding.During route redistribution, BGP can filter routing information from specificrouting protocols.Follow these steps to configure BGP route redistribution:n ■ The ORIGIN attribute of routes redistributed using the import-routecommand is Incomplete.■ The ORIGIN attribute of networks advertised into the BGP routing table withthe network command is IGP. These networks must exist in the local IP routingtable, and using a routing policy makes routes control more flexible.Configuring BGP RouteSummarizationTo reduce the routing table size on medium and large BGP networks, you need toconfigure route summarization on peers. BGP supports two summarizationmodes: automatic and manual.■ Automatic summarization: Summarizes redistributed IGP subnets. With thefeature configured, BGP advertises only summary natural networks rather thansubnets. The default route and routes injected with the network commandcan not be summarized.■ Manual summarization: Summarizes BGP local routes. The manual summaryroutes enjoy higher priority than automatic ones.Follow these steps to configure BGP route summarization:To do… Use the command… RemarksEnter system view system-view -Enter BGP view bgp as-number -Enable BGP to redistributedefault route into the BGProuting tabledefault-route imported OptionalNot enabled by defaultRedistribute routes fromanother routing protocolimport-route protocol[ process-id [ med med-value |route-policyroute-policy-name ] * ]RequiredNot redistributed by defaultInject a network to the BGProuting tablenetwork ip-address [ mask |mask-length ] [ short-cut |route-policyroute-policy-name ]OptionalNot injected by default
