Configuring The Work Mode Of An Mstp Device - HP 5820X series Configuration Manual

There is 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 selects the device with the
lowest MAC address as the root bridge.
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 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.
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:
To do...
1. Enter system view
2. Configure the current device
as the root bridge of a
specific spanning tree
Configuring the current device as a secondary root bridge of a specific spanning tree
To configure the current device as a secondary root bridge of a specific spanning tree:
To do...
1. Enter system view
2. Configure the current device
as a secondary root bridge of
a specific spanning tree
After specifying the current device as the root bridge or a secondary root bridge, you cannot change the
priority of the device.
You can also configure the current device as the root bridge by setting the priority of the device to 0. For
the device priority configuration, see

Configuring the work mode of an MSTP device

MSTP and RSTP are mutually compatible, and can recognize each other's protocol packets. However, STP
is unable to recognize MSTP packets. For hybrid networking with legacy STP devices and for full
interoperability with RSTP-enabled devices, MSTP supports the following work modes: STP-compatible
mode, RSTP mode, and MSTP mode.
In STP-compatible mode, all ports of the device send out STP BPDUs,
•
In RSTP mode, all ports of the device send out RSTP BPDUs. If the device detects that it is connected
•
to a legacy STP device, the port connecting to the legacy STP device will migrate automatically to
STP-compatible mode.
In MSTP mode, all ports of the device send out MSTP BPDUs. If the device detects that it is connected
•
to a legacy STP device, the port connecting to the legacy STP device will migrate automatically to
STP-compatible mode.
Make this configuration on the root bridge and on the leaf nodes separately.
Use the command...
system-view
stp [ instance instance-id ] root
primary
Use the command...
system-view
stp [ instance instance-id ] root
secondary
"Configuring the priority of a
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Remarks
—
Required.
By default, a device does not
function as the root bridge of any
spanning tree.
Remarks
—
Required.
By default, a device does not
function as a secondary root
bridge.
device."