H3C S9500 Series Operation Manual page 110

Operation Manual – MSTP
H3C S9500 Series Routing Switches
Table 1-4 Initial state of each device
Switch A
Switch B
Switch C
Comparison process and result on each device
The following table shows the comparison process and result on each device.
Table 1-5 Comparison process and result on each device
Device
Switch
A
Device
AP1
AP2
BP1
BP2
CP1
CP2
Comparison process
Port AP1 receives a configuration BPDU from
Switch B (that is, {1, 0, 1, BP1}). As the
configuration BPDU of the local port (that is, {0, 0,
0, AP1}) is superior to the received configuration
BPDU, the received configuration BPDU is
discarded.
Port AP2 receives a configuration BPDU from
Switch C (that is, {2, 0, 2, CP1}). As the BPDU of
the local port (that is, {0, 0, 0, AP2}) is superior to
the received configuration BPDU, the received
configuration BPDU is discarded.
Switch A finds that both the root bridge and
designated bridge in the configuration BPDUs of
all its ports are Switch A itself, so it assumes itself
to be the root bridge. In this case, it does not
make any change to the configuration BPDU of
each port, and starts sending out configuration
BPDUs periodically.
Port ID
1-7
Chapter 1 MSTP Configuration
BPDU of the port
{0, 0, 0, AP1}
{0, 0, 0, AP2}
{1, 0, 1, BP1}
{1, 0, 1, BP2}
{2, 0, 2, CP1}
{2, 0, 2, CP2}
BPDU of the port
after comparison
AP1: {0, 0, 0, AP1}
AP2: {0, 0, 0, AP2}