Administrator Guide

• You can clear the Error Disabled state with any of the following methods:
• Perform a shutdown command on the interface.
• 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 system
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 configure 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 different 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 misconfigurations.
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 differentiate
BPDUs on each VLAN so that PVST+ does not detect a loop and both ports can remain in a Forwarding state.
Figure 106. PVST+ with Extend System ID
• Augment the bridge ID with the VLAN ID.
PROTOCOL PVST mode
extend system-id
Dell(conf-pvst)#do show spanning-tree pvst vlan 5 brief
VLAN 5
Executing IEEE compatible Spanning Tree Protocol
Root ID Priority 32773, Address 0001.e832.73f7
Root Bridge hello time 2, max age 20, forward delay 15
642
Per-VLAN Spanning Tree Plus (PVST+)