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