Configuring MAC Duplication Suppression for EVPN

When PEs are interconnected both through network-side and access-side links, MAC route flapping may occur. To resolve this issue, you can configure MAC duplication suppression.

Usage Scenario

On the EVPN E-LAN shown in Figure 1, the two PEs may be interconnected both through network-side and access-side links. If this is the case, a BUM traffic loop and MAC route flapping both occur, preventing devices from working properly. By default, MAC duplication suppression is enabled on a device. Also by default, the system checks the number of times a MAC entry flaps within a detection period. If the number of MAC flaps exceeds the upper threshold, the system considers MAC route flapping to be occurring on the network and consequently suppresses the flapping MAC routes. The suppressed MAC routes cannot be sent to a remote PE through a BGP EVPN peer relationship.

Figure 1 MAC duplication suppression for EVPN

If you want to modify parameter configurations related to MAC duplication suppression, perform the following procedure.

Pre-configuration Tasks

Before configuring MAC duplication suppression, Configuring BD-EVPN Functions or Configuring Common EVPN Functions must have been performed on the network.

Procedure

Configure MAC duplication suppression for all EVPN instances.
1. Run system-view
  The system view is displayed.
2. Run evpn
  The global EVPN configuration view is displayed.
3. Run mac-duplication
  The EVPN-MAC-duplication view is displayed.
4. Run detect loop-times loop-times detect-cycle detect-cycle-time
  Loop detection parameters for MAC duplication suppression are configured, including the detection period and the threshold for the number of MAC entry flaps within a detection period. The default detection period is 180s, and the default threshold is 5.
5. Run retry-cycle retry-times
  A hold-off time to unsuppress MAC routes is configured.
6. (Optional) To disable MAC address migration suppression globally, perform the following steps:
  1. Run quit
    The EVPN global configuration view is displayed.
  2. Run undo mac-duplication
    The MAC mobility suppression is disabled globally.
7. Run commit
  The configuration is committed.
Configure MAC duplication suppression for a specified EVPN instance.
1. Run system-view
  The system view is displayed.
2. Run either of the following commands:
  - evpn vpn-instance vpn-instance-name
    
    The view of an EVPN instance is displayed.
  - evpn vpn-instance vpn-instance-name bd-mode
    
    The view of a BD-EVPN instance is displayed.
3. Run mac-duplication
  The EVPN instance MAC-duplication view is displayed.
4. Run detect loop-times loop-times detect-cycle detect-cycle-time
  Loop detection parameters for MAC duplication suppression are configured, including the detection period and the threshold for the number of MAC entry flaps within a detection period.
5. Run retry-cycle retry-times
  A hold-off time to unsuppress MAC routes is configured.
6. Run black-hole-dup-mac [ block-source-interface ]
  The flapping MAC routes are set to black-hole MAC routes. If the source or destination MAC address of the forwarded traffic is the same as the MAC address of the black-hole MAC route, the traffic is discarded.
  
  The block-source-interface parameter enables AC interface blocking. This means that, if the traffic comes from a local AC interface and the source MAC address of the traffic is the same as the MAC address of a black-hole MAC route, the AC interface is blocked. In this way, a loop can be removed quickly.
  
  Only BD-EVPN instances support AC interface blocking.
  
  To enable AC interface blocking, first enable MAC flapping-based loop detection in the BD.
7. (Optional) To disable the function of MAC duplication suppression for the current EVPN instance, run the following steps:
  1. Run quit
    Return the EVPN instance or BD-EVPN instance view.
  2. Run mac-duplication disable
    The function of MAC duplication suppression for the current EVPN instance is disabled.
8. Run commit
  The configuration is committed.

Follow-up Procedure

When a MAC route to a specific MAC address or MAC routes in a specific BD have stopped flapping and you want to restore them before the configured hold-off timer expires, run the reset evpn vpn-instance vpn-instance-name mac-duplication [ bridge-domain bd-id ] [ mac-address mac-address ] command in the user view. This allows you to manually clear the suppression state of the MAC routes.

Under certain conditions, a MAC route is unsuppressed automatically. For this to take place, a static MAC address must be configured or an EVPN instance must receive a MAC address that carries the static flag. The MAC address must be the same as that of the suppressed MAC route.

Verifying the Configuration of MAC Duplication Suppression

Run the display evpn vpn-instance name vpn-instance-name mac-duplication [ bridge-domain bd-id ] [ mac-address mac-address ] command to check information about MAC duplication suppression. The command output shows parameters related to MAC duplication suppression and information about the suppressed MAC routes.