Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

To prevent issues when connectivity between peers is lost, you can designate Primary and Secondary roles for VLT peers . You can elect or configure the Primary Peer. By default, the peer with the lowest MAC address is selected as the Primary Peer.

If the VLTi link fails, the status of the remote VLT Primary Peer is checked using the backup link. If the remote VLT Primary Peer is available, the Secondary Peer disables all VLT ports to prevent loops.

If all ports in the VLTi link fail or if the communication between VLTi links fails, VLT checks the backup link to determine the cause of the failure. If the failed peer can still transmit heartbeat messages, the Secondary Peer disables all VLT member ports and any Layer 3 interfaces attached to the VLAN associated with the VLT domain. If heartbeat messages are not received, the Secondary Peer forwards traffic assumes the role of the Primary Peer. If the original Primary Peer is restored, the VLT peer reassigned as the Primary Peer retains this role and the other peer must be reassigned as a Secondary Peer. Peer role changes are reported as SNMP traps.