MSTP
Protection
Scenario
Configuration Impact
Root
protection
Due to incorrect
configurations or malicious
attacks on the network, a
root bridge may receive
BPDUs with a higher
priority than its own 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 may transfer traffic
from high-speed links to
low-speed links, causing
traffic congestion.
To address this issue, the root protection
function can be configured to protect the root
bridge by preserving the role of the
designated port. With this function, when the
designated port receives RST BPDUs with a
higher priority, the port enters the Discarding
state and does not forward the BPDUs. If the
port does not receive any RST BPDUs with a
higher priority for a certain period (double the
Forward Delay), the port transitions to the
Forwarding state.
Loop
protection
A root port or an alternate
port will age if link
congestion or a one-way link
failure occurs. After the root
port ages, a switching device
may re-select a root port
incorrectly and after the
alternate port ages, the port
enters the Forwarding state.
Loops may occur in such a
situation.
The loop protection function can be used to
prevent such network loops. If the root port
or alternate port cannot receive RST 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
Each device has a default MSTP process with the ID of 0. MSTP configurations in the system view and
interface view both belong to this process.
Pre-configuration Tasks
Before configuring MSTP protection functions on a switching device, complete the following
task:
l
Configuring basic MSTP functions
NOTE
Configure an edge port on the switching device before configuring BPDU protection.
Data Preparation
To configure MSTP protection functions on a switching device, you need the following data.
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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