Reference Guide

rootguard (C-, S-, and E-Series TeraScale only) Enter the keyword
rootguard to enable root guard on an MSTP port or port-
channel interface.
Command
Modes
INTERFACE
Command
History
Version Description
9.7(0.0) Introduced on the S6000-ON.
8.4.2.1 Introduced the loopguard and rootguard options on the
E-Series TeraScale, C-Series, and S-Series.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.3.7.1 Introduced on the S4810.
8.2.1.0 Introduced the hardware shutdown-on-violation
option.
7.6.1.0 Introduced on the S-Series.
7.5.1.0 Introduced on the C-Series.
6.1.1.0 Added support for the BPDU guard.
Usage
Information
On an MSTP switch, a port configured as an edge port immediately transitions 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 you do not enable shutdown-on-violation, BPDUs are still 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.
1386
Multiple Spanning Tree Protocol (MSTP)