Cisco WS-SUP32-GE-3B Software Configuration Guide - Page 273

Chapter 17 Configuring STP and MST Displaying the MST Configuration and Status Restarting the Protocol Migration Process A switch running MST supports a built-in protocol migration feature that enables it to interoperate with 802.1D switches. If this switch receives an 802.1D configuration BPDU (a BPDU with the protocol version set to 0), it sends only 802.1D BPDUs on that port. An MST switch also can detect that a port is at the boundary of a region when it receives an 802.1D 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 MST mode if it no longer receives 802.1D BPDUs because it cannot detect whether the 802.1D switch has been removed from the link unless the 802.1D 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-tree detected-protocols privileged EXEC command. To restart the protocol migration process on a specific interface, use the clear spanning-tree detected-protocols interface interface_id privileged EXEC command. Displaying the MST Configuration and Status To display the spanning-tree status, use one or more of the privileged EXEC commands that are described in Table 17-8. Table 17-8 Commands for Displaying MST Status Command show spanning-tree mst configuration show spanning-tree mst configuration digest show spanning-tree mst instance_id show spanning-tree mst interface interface_id Purpose Displays the MST region configuration. Displays the MD5 digest included in the current MSTCI. Displays MST information for the specified instance. Displays MST information for the specified interface. OL-11439-03 Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY 17-49