Changing Bgp Timers; Enabling Bgp Neighbor Soft-Reconfiguration - Dell C9000 Series Networking Configuration Manual

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
Border Gateway Protocol IPv4 (BGPv4) 243