Reference Guide

• Port Channel interface with 10-Gigabit Ethernet = 1.
• Port Channel interface with 40-Gigabit Ethernet = 1.
loopguard Enter the keyword loopguard to enable STP loop guard on
a port or port-channel interface.
rootguard Enter the keyword rootguard to enable STP root guard on
a port or port-channel interface.
portfast
[bpduguard
[shutdown-on-
viol ation]]
Enter the keyword portfast to enable Portfast to move the
interface into Forwarding mode immediately after the root
fails.
Enter the optional keyword bpduguard to disable the port
when it receives a BPDU.
Enter the optional 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 number as the
priority. The range is zero (0) to 15. The default is 8.
Defaults cost = depends on the interface type; priority = 8
Command
Modes
INTERFACE
Command
History
Version 9.0(1.3) Introduced on the S5000.
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 stack-unit 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.
1306
Spanning Tree Protocol (STP)