7.6.3.3 Configuring Root Protection on an Interface
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 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 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
7.6.3.4 Configuring Loop Protection on an Interface
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.
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.
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
7 MSTP Configuration
Issue 01 (2014-11-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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