LACP-MAD overview

Link Aggregation Control Protocol-Multi-Active Detection (LACP-MAD) is a detection mechanism deployed by switches to recover from a breakup of the Intelligent Resilient Framework (IRF) stack due to link or other failure.

LACP-MAD is implemented by sending extended LACP data units (LACPDUs) with a type length value (TLV) that conveys the active ID of an IRF virtual device. The active ID is identical to the member ID of the master and is thus unique to the IRF virtual device. When LACP MAD detection is enabled, the members exchange their active IDs by sending extended LACPDUs.

  • When the IRF virtual device operates normally, the active IDs in the extended LACPDUs sent by all members are the same, indicating that there is no multi-active collision.

  • When there is a breakup in the IRF stack, the active IDs in the extended LACPDUs sent by the members in different IRF virtual devices are different, indicating that there are multi-active collisions.

LACP-MAD passthrough helps IRF-capable devices detect multi-access and take corrective action. These devices do not initiate transmission of LACP-MAD frames or participate in any MAD decision making process. These devices simply forward LACP-MAD TLVs received on one interface to the other interfaces on the trunk. LACP-MAD passthrough can be enabled for 24 LACP trunks. By default, LACP-MAD passthrough is disabled.