SRRP for PPPoE works in an environment where MC-LAG is enabled. For example, the standby MC-LAG link automatically puts the SRRP instance in a backup state and the active MC-LAG link puts the SRRP instance in a master state. It is important that the SRRP instance on the standby leg of the MC-LAG is forced into a SRRP backup state, or any other state that forces the downstream traffic to use the redundant interface.
Traffic destined for or from the subscriber is forwarded under the condition that the subscriber-interface is operationally UP. This applies also to shunting of downstream subscriber traffic from the standby (SRRP backup state) to active (SRRP master state) node. It is always necessary to keep the subscriber-interface operationally UP by configuring a dummy group interface with a oper-up-while-empty command under it. This is especially true for the MC-LAG which causes the messaging SAP on the standby node always to be in the INIT state. If MSAPs are used on such group interfaces, the group interfaces would be also operationally DOWN, causing the subscriber-interface to be operationally DOWN.