LACPDU Transmission on MLAG Ports

To prevent the server node from forming two separate aggregators to the MLAG peers (which could result in a loop), it is necessary that both MLAG peers transmit LACP PDUs with the same System Identifier and Actor Key. The following points discuss how the System Identifier is determined:
  • The MLAG peers must communicate at least once with each other to generate LACP PDUs on MLAG ports. If the MLAG peers do not communicate with each other, no LACP PDUs are sent out on the MLAG ports. The MLAG peers checkpoint their system MAC and checkpoint the configured MAC to the peer to determine the LACP Operational MAC.
  • If no LACP MAC is configured on the MLAG peers, the LACP Operational MAC is the MAC address of the MLAG peer that has the highest IP address for ISC control VLAN.
  • If a different LACP MAC address is configured on the MLAG peers, the configured MAC is not used. In this case, the LACP Operational MAC address is the MAC address of the MLAG peer that has the highest IP address for ISC control VLAN.
  • The configured MAC address is only used when the same MAC is configured on both the MLAG peers.