H3C S7500E-X Configuration Manual page 76

Device Comparison process
port, Device B calculates a designated port configuration
BPDU for Port B2 {0, 5, 1, Port B2}. Device B compares it
with the existing configuration BPDU of Port B2 {1, 0, 1, Port
B2}. Device B determines that the calculated one is
superior, and determines that Port B2 is the designated
port. It replaces the configuration BPDU on Port B2 with the
calculated one, and periodically sends the calculated
configuration BPDU.
Port C1 performs the following operations:
22. Receives the configuration BPDU of Port A2 {0, 0, 0,
Port A2}.
23. Determines that the received configuration BPDU is
superior to its existing configuration BPDU {2, 0, 2,
Port C1}.
24. Updates its configuration BPDU.
Port C2 performs the following operations:
25. Receives the original configuration BPDU of Port B2
{1, 0, 1, Port B2}.
26. Determines that the received configuration BPDU is
superior to the existing configuration BPDU {2, 0, 2,
Port C2}.
27. Updates its configuration BPDU.
Device C performs the following operations:
28. Compares the configuration BPDUs of all its ports.
29. Decides that the configuration BPDU of Port C1 is the
optimum.
30. Selects Port C1 as the root port with the configuration
BPDU unchanged.
Based on the configuration BPDU and path cost of the root
port, Device C calculates the configuration BPDU of Port C2
{0, 10, 2, Port C2}. Device C compares it with the existing
Device C
configuration BPDU of Port C2 {1, 0, 1, Port B2}. Device C
determines that the calculated configuration BPDU is
superior to the existing one, selects Port C2 as the
designated port, and replaces the configuration BPDU of
Port C2 with the calculated one.
Port C2 performs the following operations:
31. Receives the updated configuration BPDU of Port B2
{0, 5, 1, Port B2}.
32. Determines that the received configuration BPDU is
superior to its existing configuration BPDU {0, 10, 2,
Port C2}.
33. Updates its configuration BPDU.
Port C1 performs the following operations:
34. Receives a periodic configuration BPDU {0, 0, 0, Port
A2} from Port A2.
35. Determines that it is the same as the existing
configuration BPDU.
36. Discards the received BPDU.
Device C determines that the root path cost of Port C1 is
larger than that of Port C2. The root path cost of Port C1 is
10, root path cost of the received configuration BPDU (0)
plus path cost of Port C1 (10). The root path cost of Port C2
is 9, root path cost of the received configuration BPDU (5)
63
Configuration BPDU
on ports after
comparison
•
Port C1: {0, 0, 0, Port
A2}
•
Port C2: {1, 0, 1, Port
B2}
•
Root port (Port C1):
{0, 0, 0, Port A2}
•
Designated port (Port
C2): {0, 10, 2, Port
C2}
•
Port C1: {0, 0, 0, Port
A2}
•
Port C2: {0, 5, 1, Port
B2}
•
Blocked port (Port
C1): {0, 0, 0, Port A2}
•
Root port (Port C2):
{0, 5, 1, Port B2}