Users 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, 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 congure 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 dierent 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 miscongurations.
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
dierentiate BPDUs on each VLAN so that PVST+ does not detect a loop and both ports can remain in a Forwarding state.
Figure 112. 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+ Conguration
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
Bridge ID Priority 32773 (priority 32768
sys-id-ext 5), Address 0001.e832.73f7
We are the root of Vlan 5
Configured hello time 2, max age 20, forward delay 15
Per-VLAN Spanning Tree Plus (PVST+)
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