R3721-F3210-F3171-HP High-End Firewalls Network Management Configuration Guide-6PW101

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Figure 40 The STP algorithm
• Initial state of each device
Table 13 Initial state of each device
Device Port name BPDU of
p
ort
Device A
AP1 {0, 0, 0, AP1}
AP2 {0, 0, 0, AP2}
Device B
BP1 {1, 0, 1, BP1}
BP2 {1, 0, 1, BP2}
Device C
CP1 {2, 0, 2, CP1}
CP2 {2, 0, 2, CP2}
• Comparison process and result on each device
Table 14 Comparison process and result on each device
Device Comparison process
BPDU of port after
com
p
arison
Device A
• Port AP1 receives the configuration BPDU of Device B {1, 0, 1,
BP1}. Device A finds that the configuration BPDU of the local
port {0, 0, 0, AP1} is superior to the received configuration
BPDU, and discards the received configuration BPDU.
• Port AP2 receives the configuration BPDU of Device C {2, 0, 2,
CP1}. Device A finds that the BPDU of the local port {0, 0, 0,
AP2} is superior to the received configuration BPDU, and
discards the received configuration BPDU.
• Device A finds that both the root bridge and designated bridge
in the configuration BPDUs of all its ports are itself, so it assumes
itself to be the root bridge. It does not make any change to the
configuration BPDU of each port, and starts sending out
configuration BPDUs periodically.
AP1: {0, 0, 0, AP1}
AP2: {0, 0, 0, AP2}