receive BPDUs from the upstream because of link congestion or unidirectional-link failure, the
switching device selects a new root port. The original root port becomes a designated port, and
the original blocked ports change to the Forwarding state, which may cause loops on the network.
To prevent such a problem, configure loop protection.
If the root port or alternate port does not receive BPDUs from the upstream device for a long
time, the switch enabled with loop protection sends a notification to the NMS. If the root port
is used, the root port enters the Discarding state and becomes the designated port. If the alternate
port is used, the alternate port keeps blocked and becomes the designated port. In this case, loops
will not occur. After the link is not congested or unidirectional link failures are rectified, the port
receives BPDUs for negotiation and restores its original role and status.
Procedure
Step 1 Run:
system-view
The system view is displayed.
Step 2 Run:
interface interface-type interface-number
The view of the root port or alternate port is displayed.
Step 3 Run:
stp loop-protection
Loop protection is enabled on the root port ore alternate port.
By default, loop protection is disabled on a port.
NOTE
An alternate port is a backup for a root port. If a switching device has an alternate port, configure loop
protection on both the root port and the alternate port.
Root protection and loop protection cannot be configured on the same port.
----End
6.6.4.5 Checking the Configuration
Procedure
l Run the display stp [ interface interface-type interface-number ] [ brief ] command to
view the spanning tree status and statistics.
----End
6.6.5 Setting Parameters for Interoperation Between Huawei and
Non-Huawei Devices
To implement interoperation between Huawei and non-Huawei devices, select the fast transition
mode based on the Proposal/Agreement mechanism of the non-Huawei device.
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
6 STP/RSTP Configuration
Issue 01 (2014-11-30) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
209
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