1-19
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.
z 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.
z 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
current device
stp [ instance instance-id ]
priority priority
Required
The default bridge priority of a
device is 32,768.
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.
z 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.