Dell S4820T, Configuration Manual

Page: 250 / 1178

Changing BGP Timers
To configure BGP timers, use either or both of the following commands.
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 are 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.
• 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 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.
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 reevaluated. With this
command, the replay and update process is triggered only if a route-refresh request is not negotiated
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Border Gateway Protocol IPv4 (BGPv4)