H3C S5120-SI Series Configuration Guide

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Configuring the current device as the root bridge of a specific spanning tree
Follow these steps to configure the current device as the root bridge of a specific spanning tree:
To do... Use the command... Remarks
Enter system view
system-view
—
Configure the current device as
the root bridge of a specific
spanning tree
stp [ instance instance-id ]
root primary
Required
By default, a device does not
function as the root bridge of
any spanning tree.
Configuring the current device as a secondary root bridge of a specific spanning tree
Follow these steps to configure the current device as a secondary root bridge of a specific spanning
tree:
To do... Use the command... Remarks
Enter system view
system-view
—
Configure 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.
z After specifying the current device as the root bridge or a secondary root bridge, you cannot
change the priority of the device.
z Alternatively, 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, refer to Configuring the Priority of a Device
.
Configuring the Work Mode of an MSTP Device
Being mutually compatible, MSTP and RSTP 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 three work modes: STP-compatible mode,
RSTP mode, and MSTP mode.
z In STP-compatible mode, all ports of the device send out STP BPDUs,
z In RSTP mode, all ports of the device send out RSTP BPDUs. If the device detects that it is
connected with a legacy STP device, the port connecting with the legacy STP device will
automatically migrate to STP-compatible mode.
z In MSTP mode, all ports of the device send out MSTP BPDUs. If the device detects that it is
connected with a legacy STP device, the port connecting with 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:

H3C S5120-SI Series Specifications

General

Brand	H3C
Model	S5120-SI Series
Category	Switch
Language	English