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

clear spanning-tree detected-protocols

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.
This command is available only if your switch is running the enhanced software image (EI).
Syntax Description
interface interface-id
Command Modes
Privileged EXEC
Command History Release
12.1(9)EA1
Usage Guidelines
A switch running both the Multiple Spanning Tree Protocol (MSTP) and the Rapid Spanning Tree
Protocol (RSTP) supports a built-in protocol migration mechanism that enables it to interoperate with
legacy 802.1D switches. If an MSTP and RSTP 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 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
Catalyst 2950 Desktop Switch Command Reference
2-20
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; do not enter leading zeros. The valid
port-channel range is 1 to 6.
Modification
This command was first introduced.
Chapter 2 Cisco IOS Commands
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