Chapter 29
| IP Routing Commands
Border Gateway Protocol (BGPv4)
– 935 –
bgp dampening This command configures route dampening to reduce the propagation of unstable
routes. Use the no form to restore the default settings.
Syntax
bgp dampening [half-life [reuse-limit [suppress-limit
max-suppress-time]]]
no dampening
half-life – The time after which a penalty is reduced. The penalty value is
reduced to half of the previous value after the half-life time expires.
(Range: 1-45 minutes)
reuse-limit – The point at which the penalty for a flapping route must fall
before a route is unsuppressed. (Range: 1-2000)
suppress-limit – The point at which to start suppressing a route.
(Range: 1-2000)
max-suppress-time – The maximum time a route can be suppressed.
(Range: 1-255 minutes)
Command Mode
Router Configuration
Default Setting
half-life: 15 minutes
reuse-limit: 750
suppress-limit: 2000
max-suppress-time: 60 minutes (4 x half-life)
Command Usage
◆ Route dampening is used to reduce the frequency of routing updates due to
unstable routes. Dampened routes are not used in the BGP decision process
nor installed in the routing table.
◆ Each time a route flaps, the router assigns the route a penalty of 1000. If BGP
receives an attribute change, BGP increases the penalty by 500. Penalties are
cumulative, and the penalty for the route is stored in the BGP routing table until
it exceeds the suppress limit. At that point, the route state changes to damped.
◆ Note that route dampening only applies to external BGP routes.
Example
Console(config-router)#bgp dampening 20 1200 20000 220
Console(config-router)#
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