Command Line Reference Guide

shutdown-on-
violation
(OPTIONAL) Enter the keywords shutdown-on-violation to
hardware disable an interface when a BPDU is received and the port
is disabled.
priority priority Enter keyword priority followed by a value in increments of 16 as
the priority. The range is 0 to 240. The default is
128.
loopguard Enter the keyword loopguard to enable loop guard on an RSTP
port or port-channel interface.
rootguard Enter the keyword rootguard to enable root guard on an RSTP port
or port-channel interface.
Defaults Not configured.
Command Modes INTERFACE
Command History
Version 9.0(1.3) Introduced on the S5000.
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 an 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 an RSTP switch, immediately transitions to
the Forwarding state. You should only configure ports connected to end-hosts as edge
ports. 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 stack-unit CPU.
You cannot enable STP 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 displays: % Error: RootGuard is configured. Cannot
configure LoopGuard.
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)#interface tengigabitethernet 4/0
FTOS(conf-if-te-4/0)#spanning-tree rstp edge-port
FTOS(conf-if-te-4/0)#show config
!
interface TenGigabitEthernet 4/0
no ip address
switchport
spanning-tree rstp edge-port
no shutdown
FTOS#
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