H3C Technologies H3C SecPath F1000-E - Manual (Page 83)

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• Designated port ID—Designated port priority plus port name.
• Message age—Age of the configuration BPDU while it propagates in the network.
• Max age—Maximum age of the configuration BPDU can be maintained on a device.
• Hello time—Configuration BPDU interval.
• Forward delay—The delay used by STP bridges to transit the state of the root and designated ports
to forwarding.
NOTE:
For simplicity, the descriptions and examples in this document involve only the following fields in the
configuration BPDUs:
• Root bridge ID (represented by device priority)
• Root path cost
• Designated bridge ID (represented by device priority)
• Designated port ID (represented by port name)
Calculation process of the STP algorithm
• Initial state
Upon initialization of a device, each port generates a BPDU with itself as the root bridge, in which
the root path cost is 0, designated bridge ID is the device ID, and the designated port is the local
port.
• Selection of the optimum configuration BPDU
Each device sends out its configuration BPDU and receives configuration BPDUs from other
devices.
Table 10 Selection of the optimum configuration BPDU
Step Actions
1
Upon receiving a configuration BPDU on a port, the device performs the following:
• If the received configuration BPDU has a lower priority than that of the configuration BPDU
generated by the port, the device discards the received configuration BPDU and does not
process the configuration BPDU of this port.
• If the received configuration BPDU has a higher priority than that of the configuration BPDU
generated by the port, the device replaces the content of the configuration BPDU generated
by the port with the content of the received configuration BPDU.
2
The device compares the configuration BPDUs of all the ports and chooses the optimum
configuration BPDU.