The dampening command enables MBGP route dampening or modifies route dampening parameters for the MBGP routes that meet the filtering policy.
The undo dampening command restores the default configuration.
By default, route dampening is disabled.
| Parameter | Description | Value |
|---|---|---|
| half-life-reach |
Specifies a half-life for reachable routes. |
The value is an integer ranging from 1 to 45, in minutes. The default value is 15, in minutes. |
| reuse |
Specifies a Reuse value. If the penalty value of a route falls below the Reuse value, the route is reused. |
The value is an integer ranging from 1 to 20000. The default value is 750. |
| suppress |
Specifies a Suppress value. If the penalty value of a route exceeds the Suppress value, the route is dampened. |
The value is an integer ranging from 1 to 20000. The default value is 2000. The configured value must be greater than that of reuse. |
| ceiling |
Specifies a penalty ceiling. |
The value is an integer ranging from 1001 to 20000. The configured value must be greater than that of suppress. The default value is 16000. |
| route-policy route-policy-name |
Specifies the name of a routing policy. |
The name is a string of 1 to 200 case-sensitive characters, with spaces not supported. When double quotation marks are used around the string, spaces are allowed in the string. |
| route-filter route-filter-name |
Specifies the name of a route-filter. |
The value is a string of 1 to 200 case-sensitive characters, spaces not supported. If parameters are included in the referenced route-filter, specify values for them in the format of (var1, var2, ...var8) behind the route-filter name. A maximum of eight parameters can be specified, and each value ranges from 1 to 200 characters. |
| update-standard |
Enables MBGP to add a penalty value (500) to the route carried in each received Update message (excluding Withdraw message). |
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Usage Scenario
If the suppression policy for route dampening is configured, routes preferentially match suppression parameters defined by route-policy in the command.
The dampening command is valid only for EBGP routes. If no optional parameter is configured in the command, the default value of each parameter is used. The four parameters of the command are mutually dependent. If you configure one of the parameters, the other parameters also need to be configured in the command. MBGP route flap dampening measures the stability of a route by using a penalty value. The greater the penalty value, the less stable a route. Each time a route flaps, the device receives a Withdraw packet and MBGP adds a penalty value (1000) for the route. If the penalty value of a route exceeds the Suppress value, the route is dampened. The device does not add the route to the IP routing table or advertise any Update packet to other MBGP peers. MBGP strips off the best flag of the route. If the route is marked with the d flag, the last packet received by the device is an Update packet; if the route is marked with the h flag, the last packet received by the device is a Withdraw packet. After the penalty value reaches a certain limit, it does not increase any more. The limit is called the penalty ceiling. After the route is suppressed for a certain period, the penalty value is reduced by half. If the penalty value of a route marked with the d flag decreases to the reuse threshold, the d flag is removed, and the route becomes available and is selected preferentially. After that, the route can be added to the IP routing table and used to send Update packets to other MBGP peers. If the penalty value of a route marked with the h flag decreases to 0, the route is deleted from the MBGP routing table.Configuration Impact
If the dampening command is run multiple times, the latest configuration overrides the previous ones.
After the dampening command is run, the system suppresses unstable routes. This means that the system does not add unstable routes to the MBGP routing table or advertise them to other MBGP peers.Precautions
When configuring MBGP route flap dampening, note the following points: