Administrator Guide
– Disable the shutdown-on-violation command on the interface (the no spanning-tree stp-id portfast
[bpduguard | [shutdown-on-violation]] command).
– Disable spanning tree on the interface (the no spanning-tree command in INTERFACE mode).
– Disabling global spanning tree (the no spanning-tree command in CONFIGURATION mode).
PVST+ in Multi-Vendor Networks
Some non-Dell Networking systems which have hybrid ports participating in PVST+ transmit two kinds of BPDUs: an 802.1D BPDU
and an untagged PVST+ BPDU.
Dell Networking systems do not expect PVST+ BPDU (tagged or untagged) on an untagged port. If this situation occurs, the Dell
Networking OS places the port in an Error-Disable state. This behavior might result in the network not converging. To prevent the
system from executing this action, use the no spanning-tree pvst err-disable cause invalid-pvst-bpdu
command. After you congure this command, if the port receives a PVST+ BPDU, the BPDU is dropped and the port remains
operational.
Enabling PVST+ Extend System ID
In the following example, ports P1 and P2 are untagged members of dierent VLANs. These ports are untagged because the hub is
VLAN unaware. There is no data loop in this scenario; however, you can employ PVST+ to avoid potential miscongurations.
If you enable PVST+ on the Dell Networking switch in this network, P1 and P2 receive BPDUs from each other. Ordinarily, the Bridge
ID in the frame matches the Root ID, a loop is detected, and the rules of convergence require that P2 move to blocking state
because it has the lowest port ID.
To keep both ports in a Forwarding state, use extend system ID. Extend system ID augments the bridge ID with a VLAN ID to
dierentiate BPDUs on each VLAN so that PVST+ does not detect a loop and both ports can remain in a Forwarding state.
Figure 104. PVST+ with Extend System ID
• Augment the bridge ID with the VLAN ID.
PROTOCOL PVST mode
extend system-id
Example of Viewing the Extend System ID in a PVST+ Conguration
Dell(conf-pvst)#do show spanning-tree pvst vlan 5 brief
620
Per-VLAN Spanning Tree Plus (PVST+)