Dell C9000 series, Reference Manual

Page: 1649 / 2286

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
no shutdown
Dell(conf-if-te-1/1)#end
Related
Commands
show spanning-tree pvst — views the PVST+ configuration.
spanning-tree pvst err-disable
Place ports in an Err-Disabled state if they receive a PVST+ BPDU when they are members an untagged VLAN.
C9000 Series
Syntax
spanning-tree pvst err-disable cause invalid-pvst-bpdu
Defaults Enabled; ports are placed in the Err-Disabled state if they receive a PVST+ BPDU when
they are members of an untagged VLAN.
Command Modes INTERFACE
Per-VLAN Spanning Tree Plus (PVST+) 1649