Reference Guide

To configure route flap dampening parameters, set dampening parameters using a route map, clear information on route
dampening and return suppressed routes to active state, view statistics on route flapping, or change the path selection from the
default mode (deterministic) to non-deterministic, use the following commands.
● Enable route dampening.
CONFIG-ROUTER-BGP mode
bgp dampening [half-life | reuse | suppress max-suppress-time] [route-map map-name]
Enter the following optional parameters to configure route dampening parameters:
○ half-life: the range is from 1 to 45. Number of minutes after which the Penalty is decreased. After the router assigns
a Penalty of 1024 to a route, the Penalty is decreased by half after the half-life period expires. The default is 15 minutes.
○ reuse: the range is from 1 to 20000. This number is compared to the flapping route’s Penalty value. If the Penalty value
is less than the reuse value, the flapping route is once again advertised (or no longer suppressed). Withdrawn routes are
removed from history state. The default is 750.
○ suppress: the range is from 1 to 20000. This number is compared to the flapping route’s Penalty value. If the Penalty
value is greater than the suppress value, the flapping route is no longer advertised (that is, it is suppressed). The default
is 2000.)
○ max-suppress-time: the range is from 1 to 255. The maximum number of minutes a route can be suppressed. The
default is four times the half-life value. The default is 60 minutes.
○ route-map map-name: name of a configured route map. Only match commands in the configured route map are
supported. Use this parameter to apply route dampening to selective routes.
● Enter the following optional parameters to configure route dampening.
CONFIG-ROUTE-MAP mode
set dampening half-life reuse suppress max-suppress-time
○ half-life: the range is from 1 to 45. Number of minutes after which the Penalty is decreased. After the router assigns
a Penalty of 1024 to a route, the Penalty is decreased by half after the half-life period expires. The default is 15 minutes.
○ reuse: the range is from 1 to 20000. This number is compared to the flapping route’s Penalty value. If the Penalty value
is less than the reuse value, the flapping route is once again advertised (or no longer suppressed). The default is 750.
○ suppress: the range is from 1 to 20000. This number is compared to the flapping route’s Penalty value. If the Penalty
value is greater than the suppress value, the flapping route is no longer advertised (that is, it is suppressed). The default
is 2000.
○ max-suppress-time: the range is from 1 to 255. The maximum number of minutes a route can be suppressed. The
default is four times the half-life value. The default is 60 minutes.
● Clear all information or only information on a specific route.
EXEC Privilege
clear ip bgp dampening [ip-address mask]
● View all flap statistics or for specific routes meeting the following criteria.
EXEC or EXEC Privilege mode
show ip bgp flap-statistics [ip-address [mask]] [filter-list as-path-name] [regexp
regular-expression]
○ ip-address [mask]: enter the IP address and mask.
○ filter-list as-path-name: enter the name of an AS-PATH ACL.
○ regexp regular-expression: enter a regular express to match on.
By default, the path selection is deterministic, that is, paths are compared irrespective of the order of their arrival. You can
change the path selection method to non-deterministic, that is, paths are compared in the order in which they arrived
(starting with the most recent). Furthermore, in non-deterministic mode, the software may not compare MED attributes
though the paths are from the same AS.
● Change the best path selection method to non-deterministic.
Change the best path selection method to non-deterministic.
CONFIG-ROUTER-BGP mode
bgp non-deterministic-med
NOTE:
When you change the best path selection method, path selection for existing paths remains unchanged until you
reset it by entering the clear ip bgp command in EXEC Privilege mode.
Border Gateway Protocol IPv4 (BGPv4) 165