H3C S9500 Series Operation Manual page 689

Operation Manual – STP
H3C S9500 Series Routing Switches
MSTP modules communicate with each other among bridges by MSTP BPDU packets.
The following figure shows the MSTP BPDU packet format:
Figure 1-3 BPDU packet format
Figure 1-4 MSTI information format of the last part in BPDU packets
Besides field root bridge priority, root path cost, local bridge priority and port priority, the
field flags which takes one byte in an instance is also used for role selection. The
following figure describes the meaning of its eight bits:
Chapter 1 MSTP Region-configuration
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