Configuring The Root Bridge Or A Secondary Root Bridge; Configuration Restrictions And Guidelines; Configuring The Current Device As The Root Bridge Of A Specific Spanning Tree - HP 5120 EI Series Lan Switching Configuration Manual

Step
8. Display the activated
configuration
information of the MST
region.
Configuring the root bridge or a secondary root
bridge
You can have MSTP determine the root bridge of a spanning tree through MSTP calculation, or you can
specify the current device as the root bridge or as a secondary root bridge using the commands that the
system provides.
A device has independent roles in different spanning trees. It can act as the root bridge in one spanning
tree and as a secondary root bridge in another. However, one device cannot be the root bridge and a
secondary root bridge in the same spanning tree.
A spanning tree can have one root bridge only. If two or more devices are designated as the root bridge
in a spanning tree at the same time, the device with the lowest MAC address wins.
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 primary root bridge. However, if you specify a new primary
root bridge for the instance then, the one you specify, not the secondary root bridge will become the root
bridge. If you have specified multiple secondary root bridges for an instance, when the root bridge fails,
the secondary root bridge with the lowest MAC address is selected as the new root bridge.

Configuration restrictions and guidelines

You can specify one root bridge for each spanning tree, regardless of the device priority settings.
•
Once you specify a device as the root bridge or a secondary root bridge, you cannot change its
priority.
• You can configure the current device as the root bridge by setting the device priority to 0. For the
device priority configuration, see
Configuring the current device as the root bridge of a specific
spanning tree
To configure the current device as the root bridge of a specific spanning tree:
Step
1. Enter system view.
2. Configure the current device
as the root bridge.
Command
display stp region-configuration
[ | { begin | exclude | include }
regular-expression ]
"Configuring the device
Command
system-view
•
In STP/RSTP mode:
stp root primary
•
In PVST mode:
stp vlan vlan-list root primary
•
In MSTP mode:
stp [ instance instance-id ] root
primary
76
Remarks
Optional.
Available in any view
priority."
Remarks
N/A
Use one of the commands.
By default, a device does not
function as the root bridge.