Clear Spanning-Tree Detected-Protocols - Cisco Catalyst 3750 Command Reference Manual

clear spanning-tree detected-protocols

clear spanning-tree detected-protocols
Use the clear spanning-tree detected-protocols privileged EXEC command on the switch stack or on
a standalone switch 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
Defaults No default is defined.
Command Modes
Privileged EXEC
Command History Release
12.1(14)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 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 802.1D BPDUs because 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 gigabitethernet2/0/1
Related Commands Command
show spanning-tree
spanning-tree link-type
Catalyst 3750 Switch Command Reference
2-54
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
VLAN range is 1 to 4094. The port-channel range is 1 to 48.
Modification
This command was introduced.
Chapter 2
Description
Displays spanning-tree state information.
Overrides the default link-type setting and enables rapid spanning-tree
transitions to the forwarding state.
Catalyst 3750 Switch Cisco IOS Commands
78-16181-03