H3C S7500E-X Configuration Manual page 75

Device
Device C
Configuration BPDUs comparison on each device.
2.
In Table 6, each configuration BPDU contains the following fields: root bridge ID, root path cost,
designated bridge ID, and designated port ID.
Table 6 Comparison process and result on each device
Device Comparison process
Port A1 performs the following operations:
7.
8.
9.
Port A2 performs the following operations:
10. Receives the configuration BPDU of Port C1 {2, 0, 2,
Device A
11. Determines that its existing configuration BPDU {0, 0,
12. Discards the received one.
Device A determines that it is both the root bridge and
designated bridge in the configuration BPDUs of all its
ports. It considers itself as the root bridge. It does not
change the configuration BPDU of any port and starts to
periodically send configuration BPDUs.
Port B1 performs the following operations:
13. Receives the configuration BPDU of Port A1 {0, 0, 0,
14. Determines that the received configuration BPDU is
15. Updates its configuration BPDU.
Port B2 performs the following operations:
16. Receives the configuration BPDU of Port C2 {2, 0, 2,
17. Determines that its existing configuration BPDU {1, 0,
Device B
18. Discards the received BPDU.
Device B performs the following operations:
19. Compares the configuration BPDUs of all its ports.
20. Decides that the configuration BPDU of Port B1 is the
21. Selects Port B1 as the root port with the configuration
Based on the configuration BPDU and path cost of the root
Port name
Port B2
Port C1
Port C2
Receives the configuration BPDU of Port B1 {1, 0, 1,
Port B1}.
Determines that its existing configuration BPDU {0, 0,
0, Port A1} is superior to the received configuration
BPDU.
Discards the received one.
Port C1}.
0, Port A2} is superior to the received configuration
BPDU.
Port A1}.
superior to its existing configuration BPDU {1, 0, 1,
Port B1}.
Port C2}.
1, Port B2} is superior to the received configuration
BPDU.
optimum.
BPDU unchanged.
62
Configuration BPDU on
the port
{1, 0, 1, Port B2}
{2, 0, 2, Port C1}
{2, 0, 2, Port C2}
Configuration BPDU
on ports after
comparison
•
Port A1: {0, 0, 0, Port
A1}
•
Port A2: {0, 0, 0, Port
A2}
•
Port B1: {0, 0, 0, Port
A1}
•
Port B2: {1, 0, 1, Port
B2}
•
Root port (Port B1):
{0, 0, 0, Port A1}
•
Designated port (Port
B2): {0, 5, 1, Port B2}