H3C S3610-28P Operation Manual page 228

Operation Manual – MSTP
H3C S3610&S5510 Series Ethernet Switches
II. Specifying the current device as a secondary root bridge of a specific
spanning tree
Follow these steps to specify the current device as a secondary root bridge of a specific
spanning tree:
Enter system view
Specify the current device
as a secondary root
bridge of a specific
spanning tree
Note that:
Upon specifying the current device as the root bridge or a secondary root bridge,
you cannot change the priority of the device.
You can configure the current device as the root bridge or a secondary root bridge
of an MST instance, which is specified by instance instance-id in the command. If
you set instance-id to 0, the current device will be the root bridge or a secondary
root bridge of the CIST.
The current device has independent roles in different instances. It can act as the
root bridge or a secondary root bridge of one instance while it can also act as the
root bridge or a secondary root bridge of another instance. However, the same
device cannot be the root bridge and a secondary root bridge in the same instance
at the same time.
There is one and only one root bridge in effect in a spanning tree instance. If two or
more devices have been designated to be root bridges of the same spanning tree
instance, MSTP will select the device with the lowest MAC address as the root
bridge.
You can specify multiple secondary root bridges for the same instance. Namely,
you can specify secondary root bridges for the same instance on two or more than
two devices.
When the root bridge of an instance fails or is shut down, the secondary root
bridge (if you have specified one) can take over the role of the instance. However,
if you specify a new root bridge for the instance at this time, the secondary root
bridge will not become the root bridge. If you have specified multiple secondary
root bridges for an instance, when the root bridge fails, MSTP will select the
secondary root bridge with the lowest MAC address as the new root bridge.
When specifying the root bridge or a secondary root bridge, you can specify the
network diameter and hello time. However, these two options are effective only for
MST instance 0, namely the CIST. If you include these two options in your
command for any other instance, the configuration can succeed, but they will not
To do...
system-view
stp [ instance instance-id ]
root secondary
[ bridge-diameter
bridge-number ] [ hello-time
centi-seconds ]
Use the command...
1-22
Chapter 1 MSTP Configuration
Remarks
—
Required
By default, a device
does not function as
a secondary root
bridge.