Users Guide

– as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte).
All Confederation routers must be either 4 Byte or 2 Byte. You cannot have a mix of router ASN support.
To view the conguration, use the show config command in CONFIGURATION ROUTER BGP mode.
Enabling Route Flap Dampening
When EBGP routes become unavailable, they “ap” and the router issues both WITHDRAWN and UPDATE notices.
A ap is when a route:
• is withdrawn
• is readvertised after being withdrawn
• has an attribute change
The constant router reaction to the WITHDRAWN and UPDATE notices causes instability in the BGP process. To minimize this
instability, you may congure penalties (a numeric value) for routes that ap. When that penalty value reaches a congured limit, the
route is not advertised, even if the route is up. In Dell Networking OS, that penalty value is 1024. As time passes and the route does
not ap, the penalty value decrements or is decayed. However, if the route aps again, it is assigned another penalty.
The penalty value is cumulative and penalty is added under following cases:
• 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 Withdrawn routes are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
Border Gateway Protocol IPv4 (BGPv4)
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