6-34As shown in the above figure, CE 1 and CE 2 use the same AS number of 800. If AS numbersubstitution for CE 2 is configured on PE 2, when PE 2 receives a BGP update sent from CE 1, itreplaces AS number 800 as its own AS number 100. Similar configuration should also be made on PE1.Follow these steps to configure AS number substitution for a peer/peer group:To do… Use the command… RemarksEnter system view system-view —Enter BGP view bgp as-number —Replace the AS number of a peer/peergroup in the AS_PATH attribute as the localAS numberpeer { group-name |ip-address } substitute-asOptionalNot configured by default.Improper AS number substitution configuration may cause route loops; use this command withcaution.Remove private AS numbers from updates to a peer/peer groupFollow these steps to remove private AS numbers from updates to a peer/peer group:To do… Use the command… RemarksEnter system view system-view —Enter BGP view bgp as-number —Configure BGP to remove private ASnumbers from the AS_PATH attribute ofupdates to a peer/peer grouppeer { group-name |ip-address } public-as-onlyOptionalBy default, BGP updatescarry private AS numbers.Tuning and Optimizing BGP NetworksPrerequisitesBGP connections have been created.Configuring BGP Keepalive Interval and HoldtimeAfter establishing a BGP connection, two routers send keepalive messages periodically to each otherto keep the connection. If a router receives no keepalive or update message from the peer within theholdtime, it tears down the connection.
