Reference Guide

• the lower of the holdtime values is the new holdtime value, and
• whichever is the lower value; one-third of the new holdtime value, or the configured keepalive
value is the new keepalive value.
• Configure 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.
• Configure 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-Reconfiguration
BGP soft-reconfiguration 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 effect. Such resets cause undue interruption to traffic due to hard reset of the BGP cache and the
time it takes to re-establish the session. BGP soft reconfiguration allows for policies to be applied to a
session without clearing the BGP Session. Soft-reconfiguration can be done on a per-neighbor basis and
can either be inbound or outbound.
BGP soft-reconfiguration clears the policies without resetting the TCP connection.
To reset a BGP connection using BGP soft reconfiguration, use the clear ip bgp command in EXEC
Privilege mode at the system prompt.
When you enable soft-reconfiguration 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 reconfiguration (or soft reset) without preconfiguration, 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.
Border Gateway Protocol IPv4 (BGPv4)
233