Changing Bgp Timers; Enabling Bgp Neighbor Soft-Reconfiguration - Dell Z9500 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 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.
Border Gateway Protocol IPv4 (BGPv4) 193