Clear Spanning-Tree Detected-Protocols - Cisco Catalyst 2950 Command Reference Manual

Chapter 2 Catalyst 2950 and 2955 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
12.1(20)EA2
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 an 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 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 an interface:
Switch# clear spanning-tree detected-protocols interface fastethernet0/1
OL-10102-01
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 6.
Modification
This command was introduced.
This command was added to the SI.
clear spanning-tree detected-protocols
Catalyst 2950 and Catalyst 2955 Switch Command Reference
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