Configuring Bgp Route Dampening - Huawei Quidway S3500 Series Operation Manual

Operation Manual - Routing Protocol
Quidway S3500 Series Ethernet Switches
Table 5-26 Configuring to filter the routes distributed by the BGP
Configure to filter the routes
distributed by the BGP
Cancel the filtering of the
routes distributed by the BGP
By default, the BGP will not filter the received and distributed routes.
Note:
The filter-policy import command filters BGP route received from the neighbors.
The routes that cannot pass the filter won't be added to the routing table, and won't
be advertised to the neighbors.
The filter-policy export command filters all the advertised routes, including routes
imported by using the import-route command, and BGP routes learned from the
neighbors.
If the filter-policy export command does not specify which route to be filtered, then
the all the routes imported by the import-route command and the advertised BGP
routes will be filtered.
For details, please refer to the "Configure Route Filtering" part in the "Routing Policy".

5.2.9 Configuring BGP route dampening

The main possible reason for unstable route is the intermittent disappearance and
re-emergence of the route that formerly existed in the routing table, and this situation is
called the flapping. When the flapping occurs, update packet will be propagated on the
network repeatedly, which will occupy much bandwidth and much processing time of
the router. We have to find measures to avoid it. The technology controlling unstable
route is called route dampening.
The dampening divides the route into the stable route and unstable route, the latter of
which shall be suppressed (not to be advertised). The history performance of the route
is the basis to evaluate the future stability. When the route flapping occurs, penalty will
be given, and when the penalty reaches a specific threshold, the route will be
suppressed. With time going, the penalty value will decrease according to power
function, and when it decreases to certain specific threshold, the route suppression will
be eliminated and the route will be re-advertised.
Perform the following configurations in BGP view.
Operation
Huawei Technologies Proprietary
Command
filter-policy { acl-number
ip-prefix-name } export [ routing-process ]
undo filter-policy
acl-number | ip-prefix ip-prefix-name } export
[ routing-process ]
5-15
Chapter 5 BGP Configuration
| ip-prefix