Configuring BGP Route Dampening

BGP route dampening can be configured to suppress unstable routes.

Usage Scenario

The main cause of route instability is route flapping. A route is considered to be flapping when it repeatedly appears and then disappears in the routing table. BGP is generally applied to complex networks where routes change frequently. Frequent route flapping consumes lots of bandwidth and CPU resources and even seriously affects network operations.

BGP route dampening prevents frequent route flapping by using a penalty value to measure route stability. When a route flaps for the first time, a penalty value is assigned to the route. Later, each time the route flaps, the penalty value of the route increases by a specific value. The greater the penalty value, the less stable the route. If the penalty value of a route exceeds the pre-defined threshold, the route will not be advertised until the penalty value of the route reduces to the reuse threshold.

Pre-configuration Tasks

Before configuring BGP route dampening, complete the following task:

Configure basic BGP functions.

Procedure

Run system-view
The system view is displayed.
Run bgp as-number
The BGP view is displayed.
Configuring BGP route dampening parameters
- Configuring EBGP route dampening parameters
  1. Run the ipv4-family unicast command to display the IPv4 unicast address family view.
  2. Run the dampening [ half-life-reach reuse suppress ceiling | route-policy route-policy-name | route-filter route-filter-name ] ^* [ update-standard ] command to set the EBGP route dampening parameters.
- Configuring IBGP route dampening parameters
  1. Run the ipv4-family vpnv4 command to enter the BGP-VPNv4 address family view or run the ipv6-family vpnv6 command to enter the BGP-VPNv6 address family view.
  2. Run the dampening ibgp [ half-life-reach reuse suppress ceiling | route-policy route-policy-name | route-filter route-filter-name ] ^* [ update-standard ] command to set IBGP route dampening parameters.
When you configure BGP route dampening, the values of reuse, suppress, and ceiling should meet the relationship of reuse<suppress<ceiling.

If routes are differentiated based on policies and the dampening command is run to reference a route-policy, BGP can use different route dampening parameters to suppress different routes.
Run commit
The configuration is committed.

Checking the Configurations

After BGP route dampening is configured, you can check whether the configuration is correct.

Run the display bgp routing-table flap-info [ regular-expression as-regular-expression | as-path-filter { as-path-filter-number | as-path-filter-name } | network-address [ { mask | mask-length } [ longer-match ] ] ] command to check route flapping statistics.
Run the display bgp routing-table time-range start-time end-time command to view BGP routes that flap within the specified time period.
Run the display bgp routing-table dampened command to check dampened BGP routes.
Run the display bgp routing-table dampening parameter command to check configured BGP route dampening parameters.