Users 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 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 Withdrawn routes are removed from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 [vrf vrf-name] dampening [ip-address mask]
• View all flap statistics or for specific 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.
○ regexp regular-expression: enter a regular express to match on.
By default, the path selection in Dell Networking OS 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
Border Gateway Protocol IPv4 (BGPv4)
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