H3C S5120-SI series Configuration Manual page 61

Table 11 Comparison process and result on each device
Device Comparison process
•
Port A1 receives the configuration BPDU of Port B1 {1, 0, 1, Port
B1}, finds that its existing configuration BPDU {0, 0, 0, Port A1}
is superior to the received configuration BPDU, and discards the
received one.
•
Port A2 receives the configuration BPDU of Port C1 {2, 0, 2, Port
C1}, finds that its existing configuration BPDU {0, 0, 0, Port A2}
is superior to the received configuration BPDU, and discards the
Device A
received one.
•
Device A finds that it is both the root bridge and designated
bridge in the configuration BPDUs of all its ports, and 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 receives the configuration BPDU of Port A1 {0, 0, 0, Port
A1}, finds that the received configuration BPDU is superior to its
existing configuration BPDU {1, 0, 1, Port B1}, and updates its
configuration BPDU.
•
Port B2 receives the configuration BPDU of Port C2 {2, 0, 2, Port
C2}, finds that its existing configuration BPDU {1, 0, 1, Port B2}
is superior to the received configuration BPDU, and discards the
received one.
•
Device B compares the configuration BPDUs of all its ports,
decides that the configuration BPDU of Port B1 is the optimum,
Device B
and 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}, and compares it with the existing
configuration BPDU of Port B2 {1, 0, 1, Port B2}. Device B finds
that the calculated one is superior, decides that Port B2 is the
designated port, replaces the configuration BPDU on Port B2
with the calculated one, and periodically sends the calculated
configuration BPDU.
•
Port C1 receives the configuration BPDU of Port A2 {0, 0, 0, Port
A2}, finds that the received configuration BPDU is superior to its
existing configuration BPDU {2, 0, 2, Port C1}, and updates its
configuration BPDU.
Device C
•
Port C2 receives the original configuration BPDU of Port B2 {1,
0, 1, Port B2}, finds that the received configuration BPDU is
superior to the existing configuration BPDU {2, 0, 2, Port C2},
and updates its configuration BPDU.
50
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}
•
Port C1: {0, 0, 0, Port
A2}
•
Port C2: {1, 0, 1, Port
B2}