NOTE: ARP entries learned on non-VLT, non-spanned VLANs are not synced with VLT peers.RSTP ConfigurationRSTP is supported in a VLT domain.Before you configure VLT on peer switches, configure RSTP in the network. RSTP is required for initialloop prevention during the VLT startup phase. You may also use RSTP for loop prevention in the networkoutside of the VLT port channel. For information about how to configure RSTP, Rapid Spanning TreeProtocol (RSTP).Run RSTP on both VLT peer switches. The primary VLT peer controls the RSTP states, such as forwardingand blocking, on both the primary and secondary peers. Dell Networking recommends configuring theprimary VLT peer as the RSTP primary root device and configuring the secondary VLT peer as the RSTPsecondary root device.BPDUs use the MAC address of the primary VLT peer as the RSTP bridge ID in the designated bridge IDfield. The primary VLT peer sends these BPDUs on VLT interfaces connected to access devices. The MACaddress for a VLT domain is automatically selected on the peer switches when you create the domain(refer to Enabling VLT and Creating a VLT Domain).Configure both ends of the VLT interconnect trunk with identical RSTP configurations. When you enableVLT, the show spanning-tree rstp brief command output displays VLT information (refer toVerifying a VLT Configuration).Preventing Forwarding Loops in a VLT DomainDuring the bootup of VLT peer switches, a forwarding loop may occur until the VLT configurations areapplied on each switch and the primary/secondary roles are determined.To prevent the interfaces in the VLT interconnect trunk and RSTP-enabled VLT ports from entering aForwarding state and creating a traffic loop in a VLT domain, take the following steps.1. Configure RSTP in the core network and on each peer switch as described in Rapid Spanning TreeProtocol (RSTP).Disabling RSTP on one VLT peer may result in a VLT domain failure.2. Enable RSTP on each peer switch.PROTOCOL SPANNING TREE RSTP modeno disable3. Configure each peer switch with a unique bridge priority.PROTOCOL SPANNING TREE RSTP modebridge-prioritySample RSTP ConfigurationThe following is a sample of an RSTP configuration.Using the example shown in the Overview section as a sample VLT topology, the primary VLT switchsends BPDUs to an access device (switch or server) with its own RSTP bridge ID. BPDUs generated by anRSTP-enabled access device are only processed by the primary VLT switch. The secondary VLT switchtunnels the BPDUs that it receives to the primary VLT switch over the VLT interconnect. Only the primaryVirtual Link Trunking (VLT) 835
