Cisco Systems 3750E manual Displaying the MST Configuration and Status, 19-26

Chapter 19 Configuring MSTP

Displaying the MST Configuration and Status

Restarting the Protocol Migration Process

A switch running MSTP supports a built-in protocol migration mechanism that enables it to interoperate with legacy IEEE 802.1D switches. If this switch receives a legacy IEEE 802.1D configuration BPDU (a BPDU with the protocol version set to 0), it sends only IEEE 802.1D BPDUs on that port. An MSTP switch also can 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

IEEE 802.1D BPDUs because it cannot detect whether the legacy switch has been removed from the link unless the legacy switch is the designated switch. A switch also might continue to assign a boundary role to a port when the switch to which it is connected has joined the region.

To restart the protocol migration process (force the renegotiation with neighboring switches) on the switch, use the clear spanning-treedetected-protocolsprivileged EXEC command.

To restart the protocol migration process on a specific interface, use the clear spanning-treedetected-protocols interface interface-idprivileged EXEC command.

Displaying the MST Configuration and Status

To display the spanning-tree status, use one or more of the privileged EXEC commands in Table 19-5:

Table 19-5	Commands for Displaying MST Status
Command		Purpose
show spanning-tree mst configuration		Displays the MST region configuration.
show spanning-tree mst configuration digest		Displays the MD5 digest included in the current MSTCI.
show spanning-tree mst instance-id		Displays MST information for the specified instance.
show spanning-tree mst interface interface-id		Displays MST information for the specified interface.

For information about other keywords for the show spanning-treeprivileged EXEC command, see the command reference for this release.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
19-26	OL-9775-02