Users Guide

• whichever is the lower value; one-third of the new holdtime value, or the congured keepalive value is the new
keepalive value.
• Congure timer values for a BGP neighbor or peer group.
CONFIG-ROUTER-BGP mode
neighbors {ip-address | peer-group-name} timers keepalive holdtime
– keepalive: the range is from 1 to 65535. Time interval, in seconds, between keepalive messages sent to the neighbor
routers. The default is 60 seconds.
– holdtime: the range is from 3 to 65536. Time interval, in seconds, between the last keepalive message and declaring the
router dead. The default is 180 seconds.
• Congure timer values for all neighbors.
CONFIG-ROUTER-BGP mode
timers bgp keepalive holdtime
– keepalive: the range is from 1 to 65535. Time interval, in seconds, between keepalive messages sent to the neighbor
routers. The default is 60 seconds.
– holdtime: the range is from 3 to 65536. Time interval, in seconds, between the last keepalive message and declaring the
router dead. The default is 180 seconds.
To view non-default values, use the show config command in CONFIGURATION ROUTER BGP mode or the show running-
config bgp command in EXEC Privilege mode.
Enabling BGP Neighbor Soft-Reconguration
BGP soft-reconguration allows for faster and easier route changing.
Changing routing policies typically requires a reset of BGP sessions (the TCP connection) for the policies to take eect. Such resets
cause undue interruption to trac due to hard reset of the BGP cache and the time it takes to re-establish the session. BGP soft
reconguration allows for policies to be applied to a session without clearing the BGP Session. Soft-reconguration can be done on a
per-neighbor basis and can either be inbound or outbound.
BGP soft-reconguration clears the policies without resetting the TCP connection.
To reset a BGP connection using BGP soft reconguration, use the clear ip bgp command in EXEC Privilege mode at the
system prompt.
When you enable soft-reconguration for a neighbor and you execute the clear ip bgp soft in command, the update
database stored in the router is replayed and updates are re-evaluated. With this command, the replay and update process is
triggered only if a route-refresh request is not negotiated with the peer. If the request is indeed negotiated (after execution of
clear ip bgp soft in), BGP sends a route-refresh request to the neighbor and receives all of the peer’s updates.
To use soft reconguration (or soft reset) without preconguration, both BGP peers must support the soft route refresh capability,
which is advertised in the open message sent when the peers establish a TCP session.
To determine whether a BGP router supports this capability, use the show ip bgp neighbors command. If a router supports
the route refresh capability, the following message displays: Received route refresh capability from peer.
If you specify a BGP peer group by using the peer-group-name argument, all members of the peer group inherit the
characteristic congured with this command.
• Clear all information or only specic details.
EXEC Privilege mode
clear ip bgp {* | neighbor-address | AS Numbers | ipv4 | peer-group-name} [soft [in |
out]]
– *: Clears all peers.
Border Gateway Protocol IPv4 (BGPv4)
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