Spanning Tree Commands
•Rapid Spanning Tree Protocol
RSTP supports connections to either STP or RSTP nodes by monitoring the incoming protocol messages and dynamically adjusting the type of protocol messages the RSTP node transmits, as described below:
-STP Mode – If the switch receives an 802.1D BPDU after a port’s migration delay timer expires, the switch assumes it is connected to an 802.1D bridge and starts using only 802.1D BPDUs.
-RSTP Mode – If RSTP is using 802.1D BPDUs on a port and receives an RSTP BPDU after the migration delay expires, RSTP restarts the migration delay timer and begins using RSTP BPDUs on that port.Example
The following example configures the switch to use Rapid Spanning Tree:
Console(config)#
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
seconds - Time in seconds. (Range: 4 - 30 seconds)
The minimum value is the higher of 4 or
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.
