Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised part 40 is the Cisco approved textbook to use alongside version of the Cisco Networking Academy Program CCNA 1 and CCNA 2 web-based courses. The topics covered provide you with the necessary knowledge to begin your preparation for the CCNA certification exam (640-801, or 640-821 and 640-811) and to enter the field of network administration. | B Page 359 Tuesday May 20 2003 2 53 PM Ethernet Switching 359 Figure 6-30 Transmitting Data to a Known Station 10 Mbps 10 Mbps Interface 1 2 3 4 A X B X The original transmission indicated where that MAC address came from enabling the switch to deliver traffic in the network more efficiently. Microsegmentation As technology improved it became possible to build bridges with more capability. Naturally the ultimate goal is to have only one node on each port of a bridge. This would reduce the collision domains so that collisions would be nearly nonexistent. A switch does exactly that and is simply a bridge with many ports. These small physical segments are called microsegments. Microsegmentation facilitates the creation of a dedicated segment and provides dedicated bandwidth to each user on the network. Each user receives instant access to the full bandwidth and does not have to contend for available bandwidth with other users. This means that pairs of devices on the same switch can communicate in parallel with a minimum number of collisions. Microsegmentation reduces collisions in a network and effectively increases the capacity for each station connected to the network. In addition to faster microprocessors and memory two other technological advances made switches possible. Content Addressable Memory CAM is memory that essentially works backward compared to conventional memory. Entering data into the memory returns the associated address. Using CAM allows a switch to directly find the port that is associated with a MAC address without using search algorithms. An applicationspecific integrated circuit ASIC is a device consisting of undedicated logic gates that can be programmed to perform functions at logic speeds. Operations that might have been done in software now can be done in hardware using an ASIC. The use of these technologies greatly reduced the delays caused by software processing and enabled a switch to keep pace with the data demands of many .
