The stp root primary command sets a device as the root or the secondary bridge of a spanning tree.
The undo stp root command cancels the configuration.
By default, the device does not act as the root or secondary root bridge of any spanning tree.
| Parameter | Description | Value |
|---|---|---|
| instance instance-id |
Specifies the ID of a spanning tree instance. If this parameter is not specified, the configuration takes effect on a Common and Internal Spanning Tree (CIST) instance. |
The value is an integer ranging from 0 to 4094, Value 0 indicates CIST. |
| primary |
Specifies a device as the root bridge of a spanning tree. |
- |
| secondary |
Specifies a device as the secondary root bridge of a spanning tree. |
- |
Usage Scenario
On an STP/RSTP/MSTP network, each spanning tree has only one root bridge responsible for sending Bridge Protocol Data Units (BPDUs). To configure a device with high performance and network hierarchy as the root bridge, run the stp root primary command. To ensure uninterrupted traffic forwarding, run the stp root secondary command to set a secondary root bridge. When the primary root bridge becomes faulty or is powered off, the secondary root bridge becomes the primary root bridge after the spanning tree calculation is complete.
After the stp root primary command is run to configure a device as the primary root bridge, the priority value of the device is 0 on the spanning tree. The secondary root bridge specified using the stp root secondary command has the priority value 4096.Precautions