Table 6-9
Selecting the optimal configuration BPDU
Ste
p
Process
1
Each port compares the received configuration BPDU with its own configuration
BPDU:
l
If the received configuration BPDU is inferior, the port discards the received
configuration BPDU and does retain its own configuration BPDU.
l
If the received configuration BPDU is superior, the port replaces its own
configuration BPDU with the received one.
2
The device compares configuration BPDUs on all the ports and selects the optimal
one.
Example of STP Topology Calculation
After the root bridge, root ports, and designated ports are selected successfully, a tree topology
is set up on the entire network. The following example illustrates how STP calculation is
implemented.
Figure 6-8
STP networking and calculated topology
DeviceA
DeviceC
DeviceB
DeviceA
Priority=0
DeviceC
Priority=2
DeviceB
Priority=1
Port A1
Port A2
Port C1
Port C2
Port B1
Port B2
P
at
h
co
st
=5
Path cost=4
P
ath
co
st=
10
root port
designated port
blocked port
Root
Bridge
STP Topology
Calculation
, DeviceA, DeviceB, and DeviceC are deployed on the network, with
priorities 0, 1, and 2, respectively. The path costs between DeviceA and DeviceB, DeviceA and
DeviceC, and DeviceB and DeviceC are 5, 10, and 4, respectively.
1.
Initial state of each device
lists the initial state of each 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.
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