z

z

z

You can configure a device as the root bridges of multiple spanning tree instances. But you cannot configure two or more root bridges for one spanning tree instance. So, do not configure root bridges for the same spanning tree instance on two or more devices using the stp root primary command.

You can configure multiple secondary root bridges for one spanning tree instance. That is, you can configure secondary root bridges for the same spanning tree instance on two or more devices using the stp root secondary command.

You can also configure the current device as the root bridge by setting the priority of the device to 0. Note that once a device is configured as the root bridge or a secondary root bridge, its priority cannot be modified.

Configuration example

#Configure the current device as the root bridge of spanning tree instance 1 and a secondary root bridge of spanning tree instance 2.

<device> system-view

[device] stp instance 1 root primary

[device] stp instance 2 root secondary

Configuring the Bridge Priority of the Current Device

Root bridges are selected according to the bridge priorities of the devices. You can make a specific device be selected as a root bridge by setting a lower bridge priority for it. An MSTP-enabled device can have different bridge priorities in different spanning tree instances.

Configuration procedure

Follow these steps to configure the bridge priority of the current device:

 

To do…

Use the command…

Remarks

 

 

Enter system view

system-view

 

 

 

 

 

 

 

Set the bridge priority for the

stp [ instance instance-id]

Required

 

 

The default bridge priority of a

 

 

current device

priority priority

 

 

device is 32,768.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

z

z

Once you specify a device as the root bridge or a secondary root bridge by using the stp root primary or stp root secondary command, the bridge priority of the device cannot be configured any more.

During the selection of the root bridge, if multiple devices have the same bridge priority, the one with the smallest MAC address becomes the root bridge.

1-19

Page 189
Image 189
3Com WX3000 Configuring the Bridge Priority of the Current Device, Set the bridge priority for, Stp instance instance-id