Command Line Reference Guide

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.

• 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.

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