256Controlling route distribution and receptionPrerequisitesComplete the BGP basic configuration.Configuring BGP route redistributionBGP can advertise the routing information of the local AS to peering ASs, but it redistributesrouting information from IGP into BGP rather than self finding. During route redistribution, BGPcan filter routing information from specific routing protocols.To do… Use the command… RemarksStep 1 Enter system view system-view —Step 2 Enter BGP view bgp as-number —Step 3 Enable BGP toredistribute the defaultroute into the BGProuting tabledefault-route imported OptionalNot enabled by defaultStep 4 Redistribute routes fromanother routingprotocolimport-route protocol [ process-id |all-processes ] [ med med-value |route-policy route-policy-name ] *RequiredNot redistributed bydefaultStep 5 Inject a network to theBGP routing tablenetwork ip-address [ mask | mask-length ] [ short-cut | route-policyroute-policy-name ]OptionalNot injected by default• The ORIGIN attribute of routes redistributed using the import-route command is Incomplete.• The ORIGIN attribute of networks advertised into the BGP routing table with the network command isIGP. These networks must exist in the local IP routing table. Using a routing policy makes routes controlmore flexible.Configuring BGP route summarizationTo reduce the routing table size on medium and large BGP networks, configure routesummarization on peers. BGP supports the following summarization modes:• Automatic summarization: Summarizes redistributed IGP subnets. With the featureconfigured, BGP advertises only summary natural networks rather than subnets. The defaultroute and routes injected with the network command cannot be summarized.• Manual summarization: Summarizes BGP local routes. The manual summary routes havehigher priority than automatic summary routes.
