Spanning Tree Commands

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Command Usage
If at any time the switch detects STP BPDUs, including Configuration or
Topology Change Notification BPDUs, it will automatically set the selected
interface to forced STP-compatible mode. However, you can also use the
spanning-tree protocol-migration command at any time to manually
re-check the appropriate BPDU format to send on the selected interfaces (i.e.,
RSTP or STP-compatible).
Example

show spanning-tree

This command shows the configuration for the common spanning tree (CST) or for
an instance within the multiple spanning tree (MST).
Syntax
show spanning-tree [interface | mst instance-id]
interface
ethernet unit/port
-unit - Stack unit. (Range: 1)
-port - Port number. (Range: 1-26/50)
port-channel channel-id (Range: 1-32)
instance-id - Instance identifier of the multiple spanning tree.
(Range: 0-4094, no leading zeroes)
Default Setting
None
Command Mode
Privileged Exec
Command Usage
Use the show spanning-tree command with no parameters to display the
spanning tree configuration for the switch for the Common Spanning Tree
(CST) and for every interface in the tree.
Use the show spanning-tree interface command to display the spanning tree
configuration for an interface within the Common Spanning Tree (CST).
Use the show spanning-tree mst instance_id command to display the
spanning tree configuration for an instance within the Multiple Spanning Tree
(MST).
For a description of the items displayed under “Spanning-tree information,”
see "Configuring Global Settings for STA" on page 3-147. For a description of
the items displayed for specific interfaces, see "Displaying Interface Settings
for STA" on page 3-151.
Console#spanning-tree protocol-migration eth 1/5
Console#