Command Reference Guide

Per-VLAN Spanning Tree Plus (PVST+) | 1167
If shutdown-on-violation is not enabled, BPDUs will still be sent to the RPM CPU.
Root guard and loop guard cannot be enabled 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.
Example
FTOS(conf-if-gi-1/1)#spanning-tree pvst vlan 3 cost 18000
FTOS(conf-if-gi-1/1)#end
FTOS(conf-if-gi-1/1)#show config
!
interface GigabitEthernet 1/1
no ip address
switchport
spanning-tree pvst vlan 3 cost 18000
no shutdown
FTOS(conf-if-gi-1/1)#end
FTOS#
Related
Commands
spanning-tree pvst err-disable
c e s
Place ports in an err-disabled state if they receive a PVST+ BPDU when they are members an
untagged VLAN.
Syntax
spanning-tree pvst err-disable cause invalid-pvst-bpdu
Defaults
Enabled; ports are placed in err-disabled state if they receive a PVST+ BPDU when they are
members of an untagged VLAN.
Command Modes
INTERFACE
show spanning-tree pvst View PVST+ configuration