Release 1.0
Configuring BGP
526360-001-00 Rev. B
MGBI
12-15
Route flapping
occurs when a link constantly fluctuates between being available and
unavailable. When a link changes its availability, the upstream neighbor sends an
update message to all its neighbors. These routes are advertised globally. This process
continues until the underlying problem is fixed.
Route flap dampening
is a mechanism for minimizing instability caused by route
flapping. A penalty value for a route is increased by 1000 if the route flaps and is
decreased by half after 15 minutes. Once the penalty exceeds the suppress limit of
2000, the route is no longer advertised to neighbors. (The route is
damped
.) When the
penalty for a damped route falls below the reuse limit of 750, the route is again
available.
Global Route Flap Dampening
Use the
bgp dampening
command in Router Configuration mode to globally enable
the default route flap dampening parameters for all BGP routes:
MOT(config-bgp)#
bgp dampening
Policy-based Route Flap Dampening
Use the
bgp dampening
command in Router Configuration mode to configure route
flap dampening parameters for all BGP routes or specific BGP routes by using a route
map:
MOT(config-bgp)#
bgp dampening
[<
1-45
>
<
1-2000
>
<
1-2000
>
<
1-255
>]
[
route-map
<
WORD
>]
where:
1-45
is the half-life period for the penalty enabling route flap dampening in
minutes. The default is 15 minutes.
1-2000
is the number of seconds to start reusing dampened routes. The default is
750 seconds.
1-20000
is the number of seconds to start suppressing a route. The default is 2000
seconds.
1-255
is the maximum number of minutes to suppress a stable route. The default
is four times the half-life.
WORD
is the route map name.
Example
The following commands create the route map:
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