Operation Manual – MSTP
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 MSTP Configuration
1-8
Device
Comparison process
BPDU of
port after
comparison
z
Port BP1 receives the configuration BPDU of Device
A {0, 0, 0, AP1}. Device B finds that the received
configuration BPDU is superior to the configuration
BPDU of the local port {1, 0, 1, BP1}, and updates the
configuration BPDU of BP1.
z
Port BP2 receives the configuration BPDU of Device
C {2, 0, 2, CP2}. Device B finds that the configuration
BPDU of the local port {1, 0, 1, BP2} is superior to the
received configuration BPDU, and discards the
received configuration BPDU.
BP1: {0, 0, 0,
AP1}
BP2: {1, 0, 1,
BP2}
Device
B
z
Device B compares the configuration BPDUs of all its
ports, and determines that the configuration BPDU of
BP1 is the optimum configuration BPDU. Then, it
uses BP1 as the root port, the configuration BPDUs of
which will not be changed.
z
Based on the configuration BPDU of BP1 and the
path cost of the root port (5), Device B calculates a
designated port configuration BPDU for BP2 {0, 5, 1,
BP2}.
z
Device B compares the calculated configuration
BPDU {0, 5, 1, BP2} with the configuration BPDU of
BP2. If the calculated BPDU is superior, BP2 will act
as the designated port, and the configuration BPDU
on this port will be replaced with the calculated
configuration BPDU, which will be sent out
periodically.
Root port
BP1:
{0, 0, 0, AP1}
Designated
port BP2:
{0, 5, 1, BP2}