PVST+ ConfigurationPVST+ is supported in a VLT domain.Before you configure VLT on peer switches, configure PVST+ in the network. PVST+ is required for initial loop prevention during theVLT startup phase. You may also use PVST+ for loop prevention in the network outside of the VLT port channel.Run PVST+ on both VLT peer switches. PVST+ instance will be created for every VLAN configured in the system. PVST+ instancesrunning in the Primary Peer will control the VLT-LAGs on both Primary and Secondary peers. Only the Primary VLT switchdetermines the PVST+ roles and states on VLT ports and ensures that the VLT interconnect link is never blocked. PVST+ instance inPrimary peer will send the role/state of VLT-LAGs for all VLANs to the Secondary peer. Secondary peer will use this information toprogram the hardware. PVST+ instance running in Secondary peer will not control the VLT-LAGs.Dell Networking recommends configuring the primary VLT peer as the primary root device for all the configured PVST+ Instancesand configuring the secondary VLT peer as the secondary root device for all the configured PVST+ Instances.Sample PVST+ ConfigurationThe following examples show the PVST+ configuration that you must perform on each peer switch to prevent forwarding loops.Configure PVST+ on VLT Peers to Prevent Forwarding Loops (VLT Peer 1)Dell_VLTpeer1(conf)#protocol spanning-tree pvstDell_VLTpeer1(conf-pvst)#no disableDell_VLTpeer1(conf-pvst)#vlan 1000 bridge-priority 0Configure PVST+ on VLT Peers to Prevent Forwarding Loops (VLT Peer 2)Dell_VLTpeer2(conf)#protocol spanning-tree pvstDell_VLTpeer2(conf-pvst)#no disableDell_VLTpeer2(conf-pvst)#vlan 1000 bridge-priority 4096Configure both ends of the VLT interconnect trunk with identical PVST+ configurations. When you enable VLT, the showspanning-tree pvst brief command output displays VLT information.Dell#show spanning-tree pvst vlan 1000 briefVLAN 1000Executing IEEE compatible Spanning Tree ProtocolRoot ID Priority 0, Address 90b1.1cf4.9b79Root Bridge hello time 2, max age 20, forward delay 15Bridge ID Priority 0, Address 90b1.1cf4.9b79We are the root of Vlan 1000Configured hello time 2, max age 20, forward delay 15Interface DesignatedName PortID Prio Cost Sts Cost Bridge ID PortID---------- -------- ---- ------ ----------- ------- -------------------- --------Po 1 128.2 128 188 FWD(vltI) 0 0 90b1.1cf4.9b79 128.2Po 2 128.3 128 2000 FWD(vlt) 0 0 90b1.1cf4.9b79 128.3Te 1/10 128.230 128 2000 FWD 0 0 90b1.1cf4.9b79 128.230Te 1/13 128.233 128 2000 FWD 0 0 90b1.1cf4.9b79 128.233InterfaceName Role PortID Prio Cost Sts Cost Link-type Edge---------- ------ -------- ---- ------- ----------- ------- --------- ----Po 1 Desg 128.2 128 188 FWD 0 (vltI)P2P NoPo 2 Desg 128.3 128 2000 FWD 0 (vlt) P2P NoTe 1/10 Desg 128.230 128 2000 FWD 0 P2P YesTe 1/13 Desg 128.233 128 2000 FWD 0 P2P NoDell#768 Virtual Link Trunking (VLT)
