Configuring the work mode of an MSTP device
MSTP and RSTP are mutually compatible and can recognize each other’s protocol packets. However, STP
cannot 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 STP BPDUs,
•
In RSTP mode, all ports of the device send RSTP BPDUs. If the device detects that it is connected to
a legacy STP device, the port that connects to the legacy STP device will automatically migrate to
STP-compatible mode.
•
In MSTP mode, all ports of the device send MSTP BPDUs. If the device detects that it is connected to
a legacy STP device, the port that connects to the legacy STP device will automatically migrate to
STP-compatible mode.
Make this configuration on the root bridge and on the leaf nodes separately.
Follow these steps to configure the MSTP work mode:
To do...
Use the command...
Remarks
Enter system view
system-view
—
Configure the work mode of MSTP
stp mode
{
stp
|
rstp
|
mstp
}
Required
MSTP mode by default.
Configuring the priority of a device
Device priority is a factor in spanning tree calculation. The priority of a device determines whether it can
be elected as the root bridge of a spanning tree. A lower numeric value indicates a higher priority. You
can set the priority of a device to a low value to specify the device as the root bridge of the spanning tree.
An MSTP-enabled device can have different priorities in different MSTIs.
Make this configuration on the root bridge only.
Follow these steps to configure the priority of a device in a specified MSTI:
To do...
Use the command...
Remarks
Enter system view
system-view
—
Configure the priority of the current
device in a specified MSTI
stp
[
instance
instance-id
]
priority
priority
Required
32768 by default.
CAUTION:
•
You cannot change the priority of a device after it is configured as the root bridge or as a secondary root
bridge.
•
During root bridge selection, if all devices in a spanning tree have the same priority, the one with the
lowest MAC address will be selected as the root bridge of the spanning tree.
Configuring the maximum hops of an MST region
By setting the maximum hops of an MST region, you can restrict the region size. The maximum hops
configured on the regional root bridge will be used as the maximum hops of the MST region.
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