![Huawei AR530 Series Configuration Manual Download Page 238](http://html.mh-extra.com/html/huawei/ar530-series/ar530-series_configuration-manual_169308238.webp)
Purpose
After a spanning tree protocol is configured on an Ethernet switching network, it calculates the
network topology and implements the following functions to remove network loops:
l
Loop cut-off: The potential loops on the network are cut off by blocking redundant links.
l
Link redundancy: When an active path becomes faulty, a redundant link can be activated
to ensure network connectivity.
7.2 MSTP Principles
This section describes the principles of MSTP.
7.2.1 MSTP Background
RSTP, an enhancement to STP, implements fast convergence of the network topology. There is
a defect for both RSTP and STP: All VLANs on a LAN use one spanning tree, and VLAN-based
load balancing cannot be performed. Once a link is blocked, it will no longer transmit traffic,
wasting bandwidth and causing the failure in forwarding certain VLAN packets.
Figure 7-1
STP/RSTP defect
S1
S2
S3
S4
S5
S6
VLAN3
VLAN2
VLAN3
VLAN2
VLAN3
VLAN2
VLAN2
VLAN3
VLAN3
HostC
(
VLAN3
)
HostB
(
VLAN2
)
HostA
(
VLAN2
)
HostD
(
VLAN3
)
spanning tree(root bridge:S6)
VLAN2
VLAN3
VLAN2
VLAN2
VLAN3
On the network shown in
, STP or RSTP is enabled. The broken line shows the
spanning tree. S6 is the root switching device. The links between S1 and S4 and between S2 and
S5 are blocked. VLAN packets are transmitted by using the corresponding links marked with
"VLAN2" or "VLAN3."
Host A and Host B belong to VLAN 2 but they cannot communicate with each other because
the link between S2 and S5 is blocked and the link between S3 and S6 denies packets from
VLAN 2.
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.
224