Reference Guide
Multiple Spanning Tree Protocol (MSTP) | 1047
Command Modes
INTERFACE
Command
History
Usage
Information
On an MSTP switch, a port configured as an edge port will immediately transition to
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 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 an MSTP network, if root guard blocks a boundary port in the CIST,
the port is also blocked in all other MST instances.
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.
loopguard
(C-, S-, and E-Series TeraScale only) Enter the keyword loopguard to enable
STP loop guard on an MSTP port or port-channel interface.
rootguard
(C-, S-, and E-Series TeraScale only) Enter the keyword rootguard to enable
root guard on an MSTP port or port-channel interface.
Version 8.3.19.0 Introduced on S4820T
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 option
Version 7.6.1.0 Added support for S-Series
Version 7.5.1.0 Added support for C-Series
Version 6.1.1.0 Support for BPDU guard added