Spanning Tree Commands
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• Multiple Spanning Tree Protocol
- To allow multiple spanning trees to operate over the network, you must
configure a related set of bridges with the same MSTP configuration,
allowing them to participate in a specific set of spanning tree instances.
- A spanning tree instance can exist only on bridges that have compatible
VLAN instance assignments.
- Be careful when switching between spanning tree modes. Changing modes
stops all spanning-tree instances for the previous mode and restarts the
system in the new mode, temporarily disrupting user traffic.
Example
The following example configures the switch to use Rapid Spanning Tree:
spanning-tree forward-time
This command configures the spanning tree bridge forward time globally for this
switch. Use the no form to restore the default.
Syntax
spanning-tree forward-time seconds
no spanning-tree forward-time
seconds - Time in seconds. (Range: 4 - 30 seconds)
The minimum value is the higher of 4 or [(max-age / 2) + 1].
Default Setting
15 seconds
Command Mode
Global Configuration
Command Usage
This command sets the maximum time (in seconds) the root device will wait
before changing states (i.e., discarding to learning to forwarding). This delay is
required because every device must receive information about topology
changes before it starts to forward frames. In addition, each port needs time to
listen for conflicting information that would make it return to the discarding
state; otherwise, temporary data loops might result.
Example
Console(config)#spanning-tree mode rstp
Console(config)#
Console(config)#spanning-tree forward-time 20
Console(config)#