Configuring EVPN Recursion Suppression in Case of Next Hop Flapping

EVPN recursion suppression in case of next hop flapping prevents the system from processing changes in EVPN routes that recurse to a frequently flapping next hop, thereby reducing system resource consumption and CPU usage.

Context

If a large number of EVPN routes recurse to the same next hop that flaps frequently, the system will be busy processing changes in these routes, consuming excessive system resources and leading to high CPU usage. To address this issue, configure EVPN recursion suppression in case of next hop flapping.

By default, EVPN recursion suppression in case of next hop flapping is enabled. After EVPN recursion suppression in case of next hop flapping is enabled, an EVPN device determines whether to increase, retain, or reduce the penalty value by comparing the flapping interval with the configured threshold. When the penalty value exceeds 10, the EVPN device suppresses route recursion to the corresponding next hop. For example, if the intervals for increasing, retaining, and clearing the penalty value are T1, T2, and T3, respectively, the device calculates the penalty value as follows:

Increases the penalty value by 1 if the flapping interval is less than T1.
Retains the penalty value if the flapping interval is greater than or equal to T1, but less than T2.
Reduces the penalty value by 1 if the flapping interval is greater than or equal to T2, but less than T3.
Clears the penalty value if the flapping interval is greater than or equal to T3.

Pre-configuration Tasks

Before configuring EVPN recursion suppression in case of next hop flapping, complete the following task:

Configuring PBB-EVPN

Procedure

Perform the following configurations in the global EVPN configuration view:
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
3. Run nexthop recursive-lookup restrain suppress-interval add-count-time hold-interval hold-count-time clear-interval clear-count-time
  The intervals for increasing, retaining, and clearing the penalty value for EVPN recursion suppression in case of next hop flapping are configured.
4. Run quit
  Return to the system view.
5. (Optional) Run evpn
  The global EVPN configuration view is displayed.
6. (Optional) Run nexthop recursive-lookup restrain disable
  EVPN recursion in case of next hop flapping globally is disabled.
  
  If you do not want to slow down route recursion processing and high CPU usage due to route recursion change processing is not a concern, you can disable recursion suppression in case of next hop flapping. After this step is performed, recursion suppression in case of next hop flapping does not take effect for any B-EVPN instance.
7. Run commit
  The configuration is committed.
Perform the following configurations in the specified EVPN instance view:
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
3. Run nexthop recursive-lookup restrain suppress-interval add-count-time hold-interval hold-count-time clear-interval clear-count-time
  The intervals for increasing, retaining, and clearing the penalty value for EVPN recursion suppression in case of next hop flapping are configured.
4. Run quit
  Return to the system view.
5. (Optional) Run evpn vpn-instance vpn-instance-name b-evpn
  The specified B-EVPN instance view is displayed.
6. (Optional) Run nexthop recursive-lookup restrain disable
  EVPN recursion suppression in case of next hop flapping is disabled in the current B-EVPN instance.
  
  If you do not want to slow down route recursion processing and high CPU usage due to route recursion change processing is not a concern, you can disable recursion suppression in case of next hop flapping. After this step is performed, recursion suppression in case of next hop flapping does not take effect for the current B-EVPN instance.
  
  For a B-EVPN instance, EVPN recursion suppression in case of next hop flapping takes effect only when this function is enabled in both the global EVPN configuration view and B-EVPN instance view.
7. Run commit
  The configuration is committed.

Verifying the Configuration

Run the display bgp evpn { all | route-distinguisher route-distinguisher | vpn-instance vpn-instance-name } routing-table [ { ad-route | es-route | inclusive-route | mac-route } prefix ] command to check PBB-EVPN routing information.