Clear Spanning-Tree Detected-Protocols - Cisco Catalyst 3550 Command Reference Manual
Multilayer switch
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- Command reference manual (794 pages) ,
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Chapter 2
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 interfaces or on the
specified interface.
Syntax Description
interface interface-id
Command Modes
Privileged EXEC
Command History
Release
12.1(9)EA1
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 802.1D switches. If a rapid-PVST+ switch or an MSTP switch receives a legacy
802.1D configuration bridge protocol data unit (BPDU) with the protocol version set to 0, it sends only
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 an RST BPDU (version 2).
However, the switch does not automatically revert to the rapid-PVST+ or MSTP mode if it no longer
receives 802.1D BPDUs because it cannot determine 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 Fast Ethernet interface 0/1:
Switch# clear spanning-tree detected-protocols interface fastethernet0/1
78-11195-09
clear spanning-tree detected-protocols [interface interface-id]
(Optional) Restart the protocol migration process on the specified interface.
Valid interfaces include physical ports, VLANs, and port channels. The
valid VLAN range is 1 to 4094. The valid port-channel range is 1 to 64.
Modification
This command was first introduced.
clear spanning-tree detected-protocols
Catalyst 3550 Multilayer Switch Command Reference
2-45
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