H3C Technologies H3C WX6000 Series Access Controllers - Manual (Page 176)

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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:
To do... Use the command... Remarks
Enter system view system-view —
Specify the current device as a
secondary root bridge of a specific
spanning tree
stp [ instance instance-id ] root
secondary
Required
By default, a device does not
function as a secondary root
bridge.
Note that:
z
Upon specifying the current device as the root bridge or a secondary root bridge, you cannot
change the priority of the device.
z
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.
z
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.
z
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.
z
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.
z
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.
z
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 actually work. For the description of network diameter and hello time,
refer to
Configuring the Network Diameter of a Switched Network and Configuring Timers of MSTP .
z
Alternatively, you can also specify the current device as the root bridge by setting the priority of the
device to 0. For the device priority configuration, refer to
Configuring the Priority of the Current
Device .
Configuration example
# Specify the current device as the root bridge of MST instance 1 and a secondary root bridge of MST
instance 2.
<Sysname> system-view
[Sysname] stp instance 1 root primary
[Sysname] stp instance 2 root secondary