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Command
Version 8.5.1.0
History
Version 8.4.2.1
Version 8.2.1.0
Version 7.6.1.0
Version 7.5.1.0
Version 7.4.1.0
Version 6.2.1.1
Usage
The BPDU guard option prevents the port from participating in an active STP topology in case a
Information
BPDU appears on a port unintentionally, or is misconfigured, or is subject to a DOS attack. This option
places the port into an error disable state if a BPDU appears, and a message is logged so that the
administrator can take corrective action.
Note:
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 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
Figure 46-7. spanning-tree pvst vlan Command 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
show spanning-tree pvst
Commands
loopguard
Introduced the
loopguard
Introduced the
C-Series, and S-Series.
Introduced hardware shutdown-on-violation option
Support added for S-Series
Support added for C-Series
Added the optional Bridge Port Data Unit (BPDU) guard
Introduced
A port configured as an edge port, on a PVST switch, will immediately transition to
View PVST+ configuration
rootguard
and
options on the E-Series ExaScale.
rootguard
and
options on the E-Series TeraScale,
Per-VLAN Spanning Tree plus (PVST+) | 1173
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