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xStack® DGS-3620 Series Layer 3 Managed Stackable Gigabit Switch CLI Reference Guide
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Example
This command shows how to disable the comparison of the Multi Exit Discriminator (MED):
DGS-3620-28SC:admin# config bgp always_compare_med disable
Command: config bgp always_compare_med disable
Success.
DGS-3620-28SC:admin#
13-17 config bgp dampening
Description
The purpose of this command is to eliminate the dampening of routes and thus to avoid unstable
networks caused by flapping routes. The following describes the way how it is achieved.
If a prefix is removed or is added, BGP will add a penalty on the route of 1000; if an attribute of
received route changes, BGP will add a penalty on the route of 500.
Suppose that the half-life is configured to be 15min, the re-use value will be 800, and the suppress
value will be 1500.
1. When a route flaps (from up to down), add the penalty by 1000.Since the penalty is
smaller than the suppress value, BGP will work normally. It will send a withdraw message
(an update message) to the neighbors.
2. The penalty of the route will decrease as time elapses. Here we assume that it pass 7.5
minutes, then the penalty of the route is 1000-500*7.5/15=750.
3. If another flap occurs (the route change from down to up) then the penalty of the route will
be 1750 which is larger than the suppress value, and the route will be dampened. BGP will
not send an update message for this status change.
4. When the penalty of the route decreases and become smaller than the re-use value (800),
the route will not be dampened and the update message will be sent again.
Note: If the dampening ability is enabled and there are one or more dampened routes, the
dampened routes will be released to be the normal state immediately after we disable the
dampening function.
Format
config bgp dampening [route_map <map_name 16> | clear_routemap | {state [enable |
disable] | half_life <value 1-45> | reuse <value 1-20000> | suppress <value 1-20000> |
max_suppress_time <value 1-255> | un_reachability_half_life <value 1-45>}(1)]
Parameters
route_map - The route_map here is to set the dampening to be criterial.
<map_name 16> - Enter the route map name here. This name can be up to 16 characters
long.
clear_routemap - This option will withdraw the route_map configuration.
state - (Optional) Specifies the BGP dampening function’s state.
enable - Specifies that the BGP dampening function's state will be enabled.