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

Before you configure VLT on peer switches, configure RSTP in the network. RSTP is required for initial loop prevention during the VLT startup phase. You may also use RSTP for loop prevention in the network outside of the VLT port channel. For information about how to configure RSTP, Rapid Spanning Tree Protocol (RSTP) .

Run RSTP on both VLT peer switches. The primary VLT peer controls the RSTP states, such as forwarding and blocking, on both the primary and secondary peers. Dell Networking recommends configuring the primary VLT peer as the RSTP primary root device and configuring the secondary VLT peer as the RSTP secondary root device.

BPDUs use the MAC address of the primary VLT peer as the RSTP bridge ID in the designated bridge ID field. The primary VLT peer sends these BPDUs on VLT interfaces connected to access devices. The MAC address for a VLT domain is automatically selected on the peer switches when you create the domain.

Configure both ends of the VLT interconnect trunk with identical RSTP configurations. When you enable VLT, the show spanning-tree rstp brief command output displays VLT information.