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, 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 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.
714 Per-VLAN Spanning Tree Plus (PVST+)