Administrator Guide

• 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 Withdrawn routes are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 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 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 in Dell 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
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Border Gateway Protocol IPv4 (BGPv4)