H3C Technologies H3C S5560 Series Switches - Manual (Page 99)

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Table 8 Comparison process and result on each device
Device Comparison process
Configuration BPDU on
ports after comparison
Device A
Port A1 performs the following tasks:
5. Receives the configuration BPDU of Port B1 {1, 0, 1, Port
B1}.
6. Determines that its existing configuration BPDU {0, 0, 0,
Port A1} is superior to the received configuration BPDU.
7. Discards the received one.
Port A2 performs the following tasks:
8. Receives the configuration BPDU of Port C1 {2, 0, 2, Port
C1}.
9. Determines that its existing configuration BPDU {0, 0, 0,
Port A2} is superior to the received configuration BPDU.
10. 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 A1: {0, 0, 0, Port
A1}
• Port A2: {0, 0, 0, Port
A2}
Device B
Port B1 performs the following tasks:
11. Receives the configuration BPDU of Port A1 {0, 0, 0, Port
A1}.
12. Determines that the received configuration BPDU is
superior to its existing configuration BPDU {1, 0, 1, Port
B1}.
13. Updates its configuration BPDU.
Port B2 performs the following tasks:
14. Receives the configuration BPDU of Port C2 {2, 0, 2, Port
C2}.
15. Determines that its existing configuration BPDU {1, 0, 1,
Port B2} is superior to the received configuration BPDU.
16. Discards the received BPDU.
• Port B1: {0, 0, 0, Port
A1}
• Port B2: {1, 0, 1, Port
B2}
Device B performs the following tasks:
17. Compares the configuration BPDUs of all its ports.
18. Decides that the configuration BPDU of Port B1 is the
optimum.
19. Selects Port B1 as the root port with the configuration
BPDU unchanged.
Based on the configuration BPDU and path cost of the root
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.
• Root port (Port B1): {0,
0, 0, Port A1}
• Designated port (Port
B2): {0, 5, 1, Port B2}