Service Manual

Verify that the VLT LAG is up in VLT peer unit.
Dell-2#show interfaces port-channel 2 brief
Codes: L - LACP Port-channel
LAG Mode Status Uptime Ports
L 2 L2L3 up 03:43:24 Gi 1/4 (Up)
Dell-4#show interfaces port-channel 2 brief
Codes: L - LACP Port-channel
LAG Mode Status Uptime Ports
L 2 L2L3 up 03:33:31 Gi 1/18 (Up)
PVST+ Conguration
PVST+ is supported in a VLT domain.
Before you congure VLT on peer switches, congure PVST+ in the network. PVST+ is required for initial loop prevention during the
VLT 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 congured in the system. PVST+ instances
running in the Primary Peer will control the VLT-LAGs on both Primary and Secondary peers. Only the Primary VLT switch
determines the PVST+ roles and states on VLT ports and ensures that the VLT interconnect link is never blocked. PVST+ instance in
Primary peer will send the role/state of VLT-LAGs for all VLANs to the Secondary peer. Secondary peer will use this information to
program the hardware. PVST+ instance running in Secondary peer will not control the VLT-LAGs.
Dell Networking recommends conguring the primary VLT peer as the primary root device for all the congured PVST+ Instances
and conguring the secondary VLT peer as the secondary root device for all the congured PVST+ Instances.
Sample PVST+ Conguration
The following examples show the PVST+ conguration that you must perform on each peer switch to prevent forwarding loops.
Congure PVST+ on VLT Peers to Prevent Forwarding Loops (VLT Peer 1)
Dell_VLTpeer1(conf)#protocol spanning-tree pvst
Dell_VLTpeer1(conf-pvst)#no disable
Dell_VLTpeer1(conf-pvst)#vlan 1000 bridge-priority 0
Congure PVST+ on VLT Peers to Prevent Forwarding Loops (VLT Peer 2)
Dell_VLTpeer2(conf)#protocol spanning-tree pvst
Dell_VLTpeer2(conf-pvst)#no disable
Dell_VLTpeer2(conf-pvst)#vlan 1000 bridge-priority 4096
Congure both ends of the VLT interconnect trunk with identical PVST+ congurations. When you enable VLT, the show
spanning-tree pvst brief
command output displays VLT information.
Dell#show spanning-tree pvst vlan 1000 brief
VLAN 1000
Executing IEEE compatible Spanning Tree Protocol
Root ID Priority 0, Address 90b1.1cf4.9b79
Root Bridge hello time 2, max age 20, forward delay 15
Bridge ID Priority 0, Address 90b1.1cf4.9b79
We are the root of Vlan 1000
Configured hello time 2, max age 20, forward delay 15
Interface Designated
Name PortID Prio Cost Sts Cost Bridge ID PortID
---------- -------- ---- ------ ----------- ------- -------------------- --------
Po 1 128.2 128 188
FWD(vltI) 0 0 90b1.1cf4.9b79 128.2
Po 2 128.3 128 2000 FWD(vlt) 0 0 90b1.1cf4.9b79 128.3
Te 1/10 128.230 128 2000 FWD 0 0 90b1.1cf4.9b79 128.230
Te 1/13 128.233 128 2000 FWD 0 0 90b1.1cf4.9b79 128.233
Virtual Link Trunking (VLT)
819