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Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 19 Configuring Standard-Compliant IEEE MST
Displaying the MST Configuration and Status
To return the port to its default setting, use the no spanning-tree mst prestandard interface
configuration command.
Restarting the Protocol Migration Process
A router running MST supports a built-in protocol migration feature that enables it to interoperate with
802.1D routers. If this router 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 router 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 router does not automatically revert to the MST mode if it no longer receives 802.1D
BPDUs because it cannot detect whether the 802.1D router has been removed from the link unless the
802.1D router is the designated router. A router also might continue to assign a boundary role to a port
when the router to which it is connected has joined the region.
To restart the protocol migration process (force the renegotiation with neighboring routers) on the router,
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 19-5.
Tip For additional information (including configuration examples and troubleshooting information), see the
documents listed on this page:
http://www.cisco.com/en/US/products/hw/routers/ps368/tsd_products_support_series_home.html
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.
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