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over low-speed links, leading to network congestion. The root protection function on a switching
device is used to protect the root bridge by preserving the role of the designated port.
NOTE
Root protection takes effect only on designated ports.
Perform the following steps on the root bridge in an MST region.
Procedure
Step 1
Run:
system-view
The system view is displayed.
Step 2
Run:
interface
interface-type interface-number
The view of the Ethernet interface participating in STP calculation is displayed.
Step 3
Run:
stp root-protection
Root protection is configured on the switching device.
By default, root protection is disabled.
----End
8.5.5 Configuring Loop Protection on an Interface
The loop protection function suppresses loops caused by link congestion.
Context
On a network running MSTP, a switching device maintains the root port status and status of
blocked ports by receiving BPDUs from an upstream switching device. If the switching device
cannot receive BPDUs from the upstream device because of link congestion or unidirectional-
link failure, the switching device re-selects a root port. The original root port becomes a
designated port and the original blocked ports change to the Forwarding state. This switching
may cause network loops, which can be mitigated by configuring loop protection.
After loop protection is configured, if the root port or alternate port does not receive BPDUs
from the upstream switching device, the root port is blocked and the switching device notifies
the NMS that the port enters the Discarding state. The blocked port remains in the Blocked state
and no longer forwards packets. This function helps prevent loops on the network. The root port
transitions to the Forwarding state after receiving new BPDUs.
NOTE
An alternate port is a backup port for a root port. If a switching device has an alternate port, you need to
configure loop protection on both the root port and the alternate port.
Perform the following steps on the root port and alternate port on a switching device in an MST
region.
Huawei AR3200 Series Enterprise Routers
Configuration Guide - LAN
8 MSTP Configuration
Issue 02 (2012-03-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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