Huawei quidway s7700 - Configuring Loop Protection on a Port

Context
Due to incorrect configurations or malicious attacks on the network, a root bridge may receive
BPDUs with a higher priority. Consequently, the legitimate root bridge is no longer able to serve
as the root bridge, and the network topology is incorrectly changed, triggering spanning tree
recalculation. This also may cause the traffic that should be transmitted over high-speed links
to be transmitted 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 is configured on a designated port. Root protection takes effect only on a designated port.
Do as follows on the root bridge.
Procedure
Step 1 Run:
system-view
The system view is displayed.
Step 2 Run:
interface interface-type interface-number
The Ethernet interface view is displayed.
Step 3 Run:
stp root-protection
Root protection is configured on the switching device.
By default, root protection is disabled.
----End
8.4.5 Configuring Loop Protection on a Port
The loop protection function suppresses the loops caused by link congestion.
Context
On a network running RSTP, 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 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 may cause network
loops. To address such a problem, configure 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 prevents loops on the network. The root port restores the
Forwarding state after receiving new BPDUs.
Quidway S7700 Smart Routing Switch
Configuration Guide - Ethernet 8 STP/RSTP Configuration
Issue 01 (2011-07-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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