Users Guide

The EdgePort status of each interface is given in the output of the show spanning-tree pvst command, as previously shown.
Dell Networking OS Behavior: Regarding the bpduguard shutdown-on-violation command behavior:
• If the interface to be shut down is a port channel, all the member ports are disabled in the hardware.
• When you add a physical port to a port channel already in an Error Disable state, the new member port is also disabled in the hardware.
• When you remove a physical port from a port channel in an Error Disable state, the Error Disabled state is cleared on this physical port
(the physical port is enabled in the hardware).
• 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, Dell Networking
OS places the port in an Error-Disable state. This behavior might result in the network not converging. To prevent Dell Networking OS
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 107. PVST+ with Extend System ID
• Augment the bridge ID with the VLAN ID.
PROTOCOL PVST mode
610
Per-VLAN Spanning Tree Plus (PVST+)