3Com Switch 8800 Advanced Software V5 Configuration Guide

442 CHAPTER 35: BGP CONFIGURATION
■ You can specify a fake AS number to hide the real one as needed. The fake AS
number applies to EBGP peers only, that is, EBGP peers in other ASs can only
find the fake AS number.
■ The peer substitute-as command is used only in specific networking
environments. Inappropriate use of the command may cause routing loops.
Tuning and
Optimizing BGP
Networks
This task involves the following parts:
1 Configure BGP timers
After establishing a BGP connection, two routers send keepalive messages
periodically to each other to keep the connection. If a router receives no keepalive
message from the peer after the holdtime elapses, it tears down the connection.
When establishing a BGP connection, the two parties compare their holdtimes,
taking the shorter one as the common holdtime.
2 Reset BGP connections
After modifying a route selection policy, you have to reset BGP connections to
make the new one take effect, causing a short time disconnection. The current
BGP implementation supports the route-refresh capability. With this capability
enabled on all BGP routers in a network, when a policy is modified on a router, the
router advertises a route-refresh message to its peers, which then resend their
routing information to the router. Therefore, the local router can perform dynamic
route update and apply the new policy without tearing down BGP connections.
If a router not supporting route-refresh exists in the network, you need to
configure the peer keep-all-routes command to save all route updates, and then
use the refresh bgp command to soft reset BGP connections, which can refresh
the BGP routing table and apply the new policy without tearing down BGP
connections.
3 Configure BGP authentication
BGP employs TCP as the transport protocol. To enhance security, you can
configure BGP to perform MD5 authentication when establishing a TCP
connection. BGP MD5 authentication is not for BGP packets. It is used to set
passwords for TCP connections. If the authentication fails, the TCP connection can
not be established.
Prerequisites Before configuring this task, you have configured BGP basic functions
Configuration Procedure To tune and optimize BGP networks, use the following commands:
To do... Use the command... Remarks
Enter system view system-view -
Enter BGP view bgp as-number -