3Com WX3000 operation manual Classification Designated bridge Designated port

Upon network convergence, the root bridge generates and sends out configuration BPDUs periodically. Other devices just forward the configuration BPDUs received. This mechanism ensures the topological stability.

2)Root port

On a non-root bridge device, the root port is the port with the lowest path cost to the root bridge. The root port is used for communicating with the root bridge. A non-root-bridge device has one and only one root port. The root bridge has no root port.

3)Designated bridge and designated port

Refer to the following table for the description of designated bridge and designated port.

Table 1-1Designated bridge and designated port

Classification	Designated bridge	Designated port
	A designated bridge is a device that is directly	The port through which the
For a device	connected to a WX3000 series device and is	designated bridge forwards
	responsible for forwarding BPDUs to the device.	BPDUs to this device
	A designated bridge is a device responsible for	The port through which the
For a LAN		designated bridge forwards
	forwarding BPDUs to this LAN segment.
		BPDUs to this LAN segment

Table 1-1 shows designated bridges and designated ports. In the figure, AP1 and AP2, BP1 and BP2, and CP1 and CP2 are ports on Device A, Device B, and Device C respectively.

z

z

If Device A forwards BPDUs to Device B through AP1, the designated bridge for Device B is Device A, and the designated port is the port AP1 on Device A.

Two devices are connected to the LAN: Device B and Device C. If Device B forwards BPDUs to the LAN, the designated bridge for the LAN is Device B, and the designated port is the port BP2 on Device B.

Figure 1-1A schematic diagram of designated bridges and designated ports

	Device A
AP1	AP2
BP1	CP1
Device B	Device C
BP2	CP2

LAN

All the ports on the root bridge are designated ports.

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