ccna r&s certification training

ccna r&s certification training.The CAM table can be created statically or dynamically. By default, the CAM table is empty when the switch is first powered on unless you have configured a static entry in it. As traffic travels through the switch, the switch will begin creating CAM tables. This dynamic creation process is a nice feature. In the early days of bridge technology, there were only two types of bridges in use: learning and non-learning. A learning bridge works in the same way as described earlier: it looks at the source MAC address in the Ethernet frame and thus dynamically learns the location of the device. In contrast, non-learning bridges do not have dynamic learning capabilities; you must statically configure the MAC address of each device and the port to which it is connected. Obviously, if a non-learning bridge contains 1000 devices, you will be busy creating and maintaining these tables, which is a daunting task. Currently, the switch supports both dynamic learning and static configurations. Typically, static configuration is used for security reasons, which are described in Chapter 11.The switch adds the learned source MAC address and its corresponding port to the CAM table (port table, MAC address table), which allows the switch to intelligently forward frames. The switch can never learn broadcast and multicast addresses because they cannot appear in the source MAC address field of the frame header.4.4.2 Forwarding FunctionalityThe second major function of the switch is to intelligently forward traffic. After a frame is received on a port, the switch not only looks at the source MAC address to perform the learning function, it also looks at the destination MAC address to perform the forwarding function. It looks at the destination MAC address and compares it to the address in the CAM table to determine which interface should be used to forward the frame to its destination.If the destination address is found in the CAM table, the forwarding process is simple: the frame is forwarded out the port specified by the corresponding CAM entry. If the switch looks at the destination address and finds that the destination device is on the same port as the source device, the frame is discarded. One way in which this occursChapter 4 Bridges and Switches 75possible reason is that the switch port is connected to a hub to which both the source and target devices are connected. In this case, the switch should not forward the frames transmitted between these two devices to other network segments,because doing so would only waste network bandwidth. As you can see, the switch intelligently forwards traffic so that each port is a separate conflict domain.1. Frame TypesThere are three types of MAC destination addresses: unicast addresses, broadcast addresses, and multicast addresses. Depending on the type of destination address, the switch must flood frames out of all ports (except inbound ports) in some cases. For the following three types of frames, flooding is always performed.. The destination address is a broadcast address: the destination MAC address is FFFF.FFFFF.FFFFFFo . Destination address is a multicast address: destination MAC address is 0100.5E00.0000 ~0100.5E7F.FFFF.