Cisco Catalyst 250 Series Command Reference

clear spanning-tree detected-protocols
To restart the protocol migration process and force renegotiation with neighboring switches on the interface,
use the clear spanning-tree detected-protocols command in privileged EXEC mode.
clear spanning-tree detected-protocols [interface interface-id]
Syntax Description
(Optional) Restarts 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 24.
interface interface-id
Command Default
None
Command Modes
Privileged EXEC
Command History
ModificationRelease
This command was introduced.Cisco IOS 15.0(2)EX
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 method that enables it to interoperate with legacy
IEEE 802.1D switches. If a rapid-PVST+ or an MSTP switch receives a legacy IEEE 802.1D configuration
bridge protocol data unit (BPDU) with the protocol version set to 0, the switch 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).
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 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
Catalyst 2960-X Switch Layer 2 Command Reference, Cisco IOS Release 15.0(2)EX
28 OL-29043 -01
Layer 2 Commands
clear spanning-tree detected-protocols

Cisco Catalyst 250 Series Specifications

General

Brand	Cisco
Model	Catalyst 250 Series
Category	Switch
Language	English