Administrator Guide

The following is a list of the Dell Networking OS version history for this command.
Version Description
9.9(0.0) Introduced on the C9010.
9.2(1.0) Introduced on the Z9500.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.4.2.1 Introduced the loopguard and rootguard options on the E-Series TeraScale, C-
Series, and S-Series.
8.3.7.0 Introduced on the S4810.
8.2.1.0 Introduced the hardware shutdown-on-violation option.
7.6.1.0 Introduced on the S-Series.
7.5.1.0 Introduced on the C-Series.
7.4.1.0 Added the optional Bridge Port Data Unit (BPDU) guard.
6.2.1.1 Introduced.
Usage Information
The BPDU guard option prevents the port from participating in an active STP topology in case a BPDU appears on
a port unintentionally, or is misconfigured, or is subject to a DOS attack. This option places the port into the Error
Disable state if a BPDU appears, and a message is logged so that the administrator can take corrective action.
NOTE: A port configured as an edge port, on a PVST switch, immediately transitions to the
forwarding state. Only ports connected to end-hosts should be configured as an edge port.
Consider an edge port similar to a port with a spanning-tree portfast enabled.
If you do not enable shutdown-on-violation, BPDUs are still sent to the route process module (RPM) CPU.
You cannot enable root guard and loop guard at the same time on a port. For example, if you configure
loop guard on a port on which root guard is already configured, the following error message is displayed: %
Error: RootGuard is configured. Cannot configure LoopGuard.
When used in a PVST+ network, loop guard is performed per-port or per-port channel at a VLAN level. If no
BPDUs are received on a VLAN interface, the port or port-channel transitions to a Loop-Inconsistent (blocking)
state only for this VLAN.
Enabling Portfast BPDU guard and loop guard at the same time on a port results in a port that remains in a
Blocking state and prevents traffic from flowing through it. For example, when Portfast BPDU guard and loop
guard are both configured:
• If a BPDU is received from a remote device, BPDU guard places the port in an Err-Disabled Blocking state and
no traffic is forwarded on the port.
• If no BPDU is received from a remote device, loop guard places the port in a Loop-Inconsistent Blocking state
and no traffic is forwarded on the port.
On PE ports and on VP-LAGs (LAGs formed with PE ports)
• Spanning-tree with bpdu guard shutdown-on-violation is enabled by default
• No spanning tree command is valid. This command is not visible and issuing this command on VP-LAG ports
results in a failure.
-
Example
Dell(conf-if-te-1/1)#spanning-tree pvst vlan 3 cost 18000
Dell(conf-if-te-1/1)#end
Dell(conf-if-te-1/1)#show config
!
interface TenGigabitEthernet 1/1
no ip address
switchport
spanning-tree pvst vlan 3 cost 18000
Per-VLAN Spanning Tree Plus (PVST+) 1233