When an switch receives Fabric Attach element TLVs on two or more ports that have same System-Id, same SMLT-Id, and have a Connection Type of SMLT, it automatically creates a LAG consisting of those ports. These LAGs:
Do not persist after a reboot—after a reboot, TLVs must be received again to re-form the LAG.
Do not require receipt of LACP PDUs—LACP PDUs are not sent.
Require at least two ports to form the LAG— When a LAG is initially created with two ports, the lowest numbered port is chosen as the master port of the LAG. If there are three or more ports on the LAG, and the port is not the master port, it is simply removed from the LAG. If it is the master port, the lag is torn down, and then re-created with the lowest port number of the remaining ports as the master port.
Are supported in stacks—the dynamic LAG is checkpointed to support failover, etc.
A port is removed from a LAG under following circumstances:
Fabric attach is disabled using the configure fabric attach ports port disable command. If the port is active, then the next LLDP packet processing removes the port form a LAG. If the port is not active, it will be removed immediately from a LAG.
TLV with Connection Type other than MLT is received.
TLV with a System-ID that is different from the one when the LAG was created is received.
TLV with a SMLT-ID that is different from the one when the LAG was created is received.
Note
The last three situations indicate that you are not connected to same Fabric Attach server, or the same LAG on a Fabric Attach server, which are not valid scenarios.
Note
MLAG with Fabric Attach Automatic LAG is not supported in ExtremeXOS 31.1 and later. Do not enable MLAGs on ports where automatically created LAGs will be created.
