Command Reference Guide

1276 | Rapid Spanning Tree Protocol (RSTP)
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Defaults
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Command Modes
INTERFACE
Command
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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 mis-configured, 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.
If
shutdown-on-violation is not enabled, BPDUs will still be sent to the RPM CPU.
STP 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.
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.
shutdown-on-vi
olation
(OPTIONAL) Enter the keyword 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.
Range: 0 to 240
Default: 128
loopguard
(C-, S-, and E-Series TeraScale only) Enter the keyword loopguard to
enable loop guard on an RSTP port or port-channel interface.
rootguard
(C-, S-, and E-Series TeraScale only) Enter the keyword rootguard to
enable root guard on an RSTP port or port-channel interface.
Version 8.4.2.1 Introduced the loopguard and rootguard options on the E-Series TeraScale,
C-Series, and S-Series.
version 8.3.7.0 Introduced on S4810
Version 8.2.1.0 Introduced hardware shutdown-on-violation options
Version 7.6.1.0 Support added for S-Series
Version 7.5.1.0 Support added for C-Series
Version 7.4.1.0 Added the optional Bridge Port Data Unit (BPDU) guard.
Version 6.2.1.1 Introduced for E-Series
Note: A port configured as an edge port, on an RSTP switch, will immediately
transition to the forwarding state. Only ports connected to end-hosts should be
configured as edge ports. Consider an edge port similar to a port with a
spanning-tree portfast enabled.