Specifications

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Cisco ME 3400 Ethernet Access Switch Command Reference

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Chapter 2 Cisco ME 3400 Ethernet Access Switch Cisco IOS Commands

clear spanning-tree detected-protocols

Use the clear spanning-tree detected-protocols privileged EXEC command to restart the protocol

migration process (force the renegotiation with neighboring switches) on all spanning-tree interfaces or

on the specified interface.

clear spanning-tree detected-protocols [interface interface-id]

Syntax Description

Defaults No default is defined.

Command Modes Privileged EXEC

Command History

Usage Guidelines A switch running the rapid per-VLAN spanning-tree plus (rapid-PVST+) protocol or the Multiple

Spanning Tree Protocol (MSTP) supports a built-in protocol migration mechanism that enables it to

interoperate with legacy IEEE 802.1D switches. If a rapid-PVST+ switch or an MSTP switch receives a

legacy IEEE 802.1D configuration bridge protocol data unit (BPDU) with the protocol version set to 0,

it sends only IEEE 802.1D BPDUs on that port. A multiple spanning-tree (MST) switch can also detect

that a port is at the boundary of a region when it receives a legacy BPDU, an MST BPDU (Version 3)

associated with a different region, or a rapid spanning-tree (RST) BPDU (Version 2).

However, the switch does not automatically revert to the rapid-PVST+ or the MSTP mode if it no longer

receives IEEE 802.1D BPDUs. It cannot learn whether the legacy switch has been removed from the link

unless the legacy switch is the designated switch. Use the clear spanning-tree detected-protocols

command in this situation.

Examples This example shows how to restart the protocol migration process on a port:

Switch# clear spanning-tree detected-protocols interface gigabitethernet0/1

interface interface-id (Optional) Restart the protocol migration process on the specified interface.

Valid interfaces include physical network node interfaces (NNIs), enhanced

network interfaces (ENIs) on which spanning tree is enabled, VLANs, and

port channels. The VLAN range is 1 to 4094. The port-channel range is 1

to 48.

Note Spanning Tree Protocol (STP) is not supported on user network

interfaces (UNIs). Though visible in the command-line help, the

command has no effect on UNIs or on ENIs on which STP is not

enabled.

Release Modification

12.2(25)EX This command was introduced.