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Configuring Damping Parameters (Optional)

Flap damping reduces the number of update messages by marking routes as ineligible for selection as the active or preferable route. Marking routes in this way leads to some delay, or suppression, in the propagation of route information, but the result is increased network stability. You typically apply flap damping to external BGP (EBGP) routes (routes in different ASs). You can also apply flap damping within a confederation, between confederation member ASs. Because routing consistency within an AS is important, do not apply flap damping to internal BGP (IBGP) routes. (If you do, it is ignored.)

To change the default BGP flap damping values, you define actions by creating a named set of damping parameters and including it in a routing policy with the damping action. For the damping routing policy to work, you also must enable BGP route flap damping.

To configure damping, perform these steps:

  1. Navigate to the top of the configuration hierarchy in either the J-Web or CLI configuration editor.
  2. Perform the configuration tasks described in Table 108.
  3. If you are finished configuring the policy, commit the configuration.

Table 108: Creating a Policy to Accept and Apply Damping on Routes

Task

J-Web Configuration Editor

CLI Configuration Editor

Navigate to the Term level in the configuration hierarchy.

In the J-Web configuration editor hierarchy, select Policy options>Policy statement>Term.

From the top of the CLI configuration hierarchy, enter

edit policy-options policy-statement dampenpolicy1 term dampenterm1

Specify the routes to dampen.
  1. In the From option, click Configure.
  2. In the Value box, enter the prefixes you wish to dampen.
  3. In the Route filter box, click Add new entry.
  4. In the Value box, enter the prefixes you wish to dampen.
  5. Click OK.
  1. Dampen routes 172.168.0.0/16 or longer:

    set from route-filter 172.16.0.0/12 orlonger

  2. Dampen routes 192.168.0.0/16 or longer:

    set from route-filter 192.168.0.0/16 orlonger

  3. Dampen routes 10.0.0.0/8 or longer:

    set from route-filter 10.0.0.0/8 orlonger

Specify the damping parameters group to apply to the route filter.
  1. In the configuration editor hierarchy, select Policy options>Policy statement>Term.
  2. In the Then option, click Configure.
  3. In the AS path prepend box, enter the string of AS numbers to prepend. Separate each AS number with a space.
  4. Click OK.

Specify the AS numbers to prepend, and enclose inside them inside double quotation marks:

set then as-path-prepend “1 1 1 1”

Navigate to the Policy options level in the configuration hierarchy.

In the J-Web configuration editor hierarchy, select Policy options.

From the top of the CLI configuration hierarchy, enter

edit policy-options

Create a damping parameter group.
  1. In the Damping box, click Add new entry.
  2. In the Damping object name box, enter the name of the damping parameter group.
  3. Click OK.

Create and configure the damping parameter groups:

edit damping group1 half-life 30 suppress 3000 reuse 750 max-suppress 60

edit damping group2 half-life 40 suppress 400 reuse 1000 max-suppress 45

edit damping group3 disable

Configure a damping parameter group.
  1. In the Half life box, enter the half life duration, in minutes.
  2. In the Max suppress box, enter the maximum holddown time, in minutes.
  3. In the Reuse box, enter the reuse threshold, for this damping group.
  4. In the Suppress box, enter the cutoff threshold, for this damping group.
  5. To disable damping for this damping group, select the Disable check box.
  6. Click OK.

Navigate to the BGP level in the configuration hierarchy.

In the J-Web configuration editor hierarchy, select Protocols>Bgp.

From the top of the CLI configuration hierarchy, enter

edit protocols bgp

Enable damping.
  1. Select the Damping check box.
  2. Click OK.

Enable damping:

set damping

Navigate to the Neighbor level in the configuration hierarchy, for the BGP neighbor to which you want to apply the damping policy—for example, the neighbor at IP address 172.16.15.14.

In the J-Web configuration editor hierarchy, select Protocols>Bgp>Group Group1>Neighbor 172.16.15.14 .

From the top of the CLI configuration hierarchy, enter

edit protocols bgp group group1 neighbor 172.16.15.14

Apply the policy as an import policy for the BGP neighbor.
  1. In the Import box, click Add new entry.
  2. In the Value box, enter the name of the policy.
  3. Click OK.

The routing policy is evaluated when routes are imported to the routing table.

Apply the policy:

set import dampenpolicy1

You can refer to the same routing policy one or more times in the same or a different import statement.
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