Full Duplex Ethernet

Full-duplex Ethernet was explained back in Chapter 3. Briefly, when a switch port has only a single device attached to it, no collisions could possibly occur because there is only one connected device. So, the device cabled to that switch port disables its NIC loopback logic, allowing the device to both send a frame and receive a frame at the same time.

If a hub with multiple devices is connected to a switch port, collisions still can occur, so half-duplex operation must be used. Figure 9-6 summarizes the concept.

Figure 9-6 Full Duplex and Half Duplex

Fred 0200.1111.1111

Barney 0200.2222.2222

Wilma 0200.3333.3333

Figure 9-6 Full Duplex and Half Duplex

Wilma 0200.3333.3333

Fred 0200.1111.1111

Barney 0200.2222.2222

Betty 0200.4444.4444

Bridge Table

0200.1111.1111

E0

0200.2222.2222

E1

0200.3333.3333

E2

0200.4444.4444

E2

0 0

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