Reference Guide

220 | Border Gateway Protocol IPv4 (BGPv4)
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Use the show config command in CONFIGURATION ROUTER BGP mode or the show running-config
bgp
command in EXEC Privilege mode to view non-default values.
Timer values configured with the
neighbor timers command override the timer values configured with the
timers bgp command.
When two neighbors, configured with different
keepalive and holdtime values, negotiate for new values, the
resulting values will be as follows:
• 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.
BGP neighbor soft-reconfiguration
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 reconfig allows for policies to be applied to a session
without clearing the BGP Session. Soft-reconfig 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.
Use the
clear ip bgp command in EXEC Privilege mode at the system prompt to reset a BGP connection
using BGP soft reconfiguration.
timers bgp keepalive holdtime CONFIG-ROUTER-
BGP
Configure timer values for all neighbors.
•
keepalive range: 1 to 65535. Time interval, in
seconds, between keepalive messages sent to the
neighbor routers. (Default: 60 seconds)
• holdtime range: 3 to 65536. Time interval, in
seconds, between the last keepalive message and
declaring the router dead. (Default: 180 seconds)
Command Syntax Command Mode Purpose
clear ip bgp {* | neighbor-address |
AS Numbers | ipv4 | peer-group-name}
[soft [in | out]]
EXEC Privilege Clear all information or only specific details.
*: Clear all peers
neighbor-address: Clear the neighbor with this IP
address
AS Numbers: Peers’ AS numbers to be cleared
ipv4: Clear information for IPv4 Address family
peer-group-name: Clear all members of the specified
peer group
neighbor {ip-address |
peer-group-name}
soft-reconfiguration inbound
CONFIG-ROUTER-B
GP
Enable soft-reconfiguration for the BGP neighbor
specified. BGP stores all the updates received by the
neighbor but does not reset the peer-session.
Command Syntax Command Mode Purpose