Tuning and Optimizing BGP Networks 849■ The peer substitute-as command is used only in specific networkingenvironments. Inappropriate use of the command may cause routing loops.Tuning andOptimizing BGPNetworksThis task involves the following parts:1 Configure BGP timersAfter establishing a BGP connection, two routers send keepalive messagesperiodically to each other to keep the connection. If a router receives no keepalivemessage from the peer after the holdtime elapses, it tears down the connection.When establishing a BGP connection, the two parties compare their holdtimevalues, taking the shorter one as the common holdtime.2 Reset BGP connectionsAfter modifying a route selection policy, you have to reset BGP connections tomake the new one take effect, causing a short time disconnection. The currentBGP implementation supports the route-refresh capability. With this capabilityenabled on all BGP routers in a network, when a policy is modified on a router, therouter advertises a route-refresh message to its peers, which then resend theirrouting information to the router. Therefore, the local router can perform dynamicroute update and apply the new policy without tearing down BGP connections.If a router not supporting route-refresh exists in the network, you need toconfigure the peer keep-all-routes command to save all route updates, and thenuse the refresh bgp command to soft reset BGP connections, which can refreshthe BGP routing table and apply the new policy without tearing down BGPconnections.3 Configure BGP authenticationBGP employs TCP as the transport protocol. To enhance security, you canconfigure BGP to perform MD5 authentication when establishing a TCPconnection. BGP MD5 authentication is not for BGP packets. It is used to setpasswords for TCP connections. If the authentication fails, the TCP connection cannot be established.Prerequisites Before configuring this task, you have configured BGP basic functionsConfiguration Procedure To tune and optimize BGP networks, use the following commands:To do... Use the command... RemarksEnter system view system-view -Enter BGP view bgp as-number -
