Concept Guide

• Withdraw
• Readvertise
• Attribute change
When dampening is applied to a route, its path is described by one of the following terms:
• history entry — an entry that stores information on a downed route
• dampened path — a path that is no longer advertised
• penalized path — a path that is assigned a penalty
To congure route ap 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 apping, 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 congure 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 apping route’s Penalty value. If the Penalty value is less than
the reuse value, the apping 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 Withdrawn routes are removed from history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 apping route’s Penalty value. If the Penalty value is
greater than the suppress value, the apping 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 congured route map. Only match commands in the congured route map are supported. Use
this parameter to apply route dampening to selective routes.
• Enter the following optional parameters to congure 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 apping route’s Penalty value. If the Penalty value is less than
the reuse value, the apping 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 apping route’s Penalty value. If the Penalty value is
greater than the suppress value, the apping 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 specic route.
EXEC Privilege
clear ip bgp [vrf vrf-name] dampening [ip-address mask]
• View all ap statistics or for specic routes meeting the following criteria.
EXEC or EXEC Privilege mode
show ip bgp [vrf vrf-name] 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.
Border Gateway Protocol (BGP)
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