2222.22222222.2222

0200.2222.2222

Although the basic operation of bridges and switches is identical, switches do differ from

transparent bridges in some regards. Some of the differences exist just because newer features

were introduced to the market around the same time that switches became popular. Other

features, such as the optimized internal processing on switches, do create a significant

advantage to switches over bridges. Practically, the differences do not really matter because

vendors continue to improve and develop features for switches, whereas it is hard to find

vendors that offer products called bridges anymore.

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

Full Duplex Allowed

Fred

Wilma