(Optional) Configuring a Priority for a Device in an MSTI
The lower the numerical value is, the higher priority a device has and the more likely the device will be selected as a root bridge. You can configure the cost of the path from a device to the root bridge to preferentially select a root port.
Context
In a Multiple Spanning Tree Instance (MSTI), there is only one root bridge and it is the logic center of the MSTI. In root bridge selection, the device with high performance and network hierarchy is generally selected as a root bridge; however, the priority of such a device may be not that high. Thus setting a high priority for the device is necessary so that the device can function as a root bridge.
Other devices with low performance and network hierarchy are not fit to be a root bridge. Therefore, set low priorities for these devices.
Procedure
- Run system-view
The system view is displayed.
- Run stp [ instance instance-id ] priority priority
A priority is set for the device in an MSTI.
If the instance is not designated, a priority is set for the device in MSTI0.
To configure a device as a primary root bridge, you can run the stp [ instance instance-id ] root primary command directly. The priority value of this device is 0.
To configure a device as a secondary root bridge, run the stp [ instance instance-id ] root secondary command. The priority value of this device is 4096.
In an MSTI, a device cannot act as a primary root bridge and a secondary root bridge at the same time.
If you want to change the priority of a device after you run the stp [ instance instance-id ] root primary command or the stp [ instance instance-id ] root secondary command to configure the device as a primary root bridge or a secondary root bridge, disable the root bridge function or secondary root bridge function and then run the stp [ instance instance-id ] priority priority command to re-set a priority.
- Run commit
The configuration is committed.