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Version Description
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.3.10.1 Introduced the loopguard and rootguard options on the
S4810.
8.4.2.1 Introduced the loopguard and rootguard options on the
E-Series TeraScale, C-Series, and S-Series.
8.3.7.0 Introduced on the S4810.
8.2.1.0 Introduced the shutdown-on-violation option.
7.7.1.0 Introduced on the S-Series.
7.5.1.0 Introduced on the C-Series.
6.2.1.1 Introduced on the E-Series.
Usage
Information
If you enable portfast bpduguard on an interface and the interface receives a
BPDU, the software disables the interface and sends a message stating that fact.
The port is in ERR_DISABLE mode, yet appears in the show interface
commands as enabled. If you do not enable shutdown-on-violation, BPDUs
are still sent to the RPM CPU.
STP loop guard and root guard are supported on a port or port-channel enabled in
any Spanning Tree mode: Spanning Tree Protocol (STP), Rapid Spanning Tree
Protocol (RSTP), Multiple Spanning Tree Protocol (MSTP), and Per-VLAN Spanning
Tree Plus (PVST+).
Root guard is supported on any STP-enabled port or port-channel except when
used as a stacking port. When enabled on a port, root guard applies to all VLANs
configured on the port.
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
.
Do not enable Portfast BPDU guard and loop guard at the same time on a port.
Enabling both features may result 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.
To display the type of STP guard (Portfast BPDU, root, or loop guard) enabled on a
port, enter the show spanning-tree 0 command.
1782
Spanning Tree Protocol (STP)