ccna wireless practice test

ccna wireless practice test.. Failure to properly learn MAC addresses. These aspects are discussed below, and the simple network shown in Figure 13.2 is used as an example to illustrate the problems they pose.Multiple Frame Copies and Broadcast Storms Chapter 4 said that the switch floods the following three types of frames: broadcast frames, multicast frames, and unicast frames with unknown destination addresses. Layer 2 networksFlooding of broadcast and multicast can cause serious performance problems when loops exist in the network. For example, in Figure 13.2, assume that PC-A performs an ARP request to learn the MAC address of PC-B. As described in Chapter 5, the Address Resolution Protocol (ARP) uses a broadcast mechanism to learn the MAC address corresponding to an IP address. In Figure 13.2, both switches will receive this frame and flood it to segment 2, since it is a broadcast frame.Figure 13.2 Example of a simple Layer 2 loopThe first problem with this is that although PC-A only generates . PC-B treats them as two different ARP requests and in turn makes out two replies. Also, depending on the application receiving the traffic, PC-B may see multiple copies of the same frame as errors and reset the connection to the source device, causing connectivity problems.The bigger problem, however, is that both switches will again see ARP requests flooded on their ports on segment 2 and flood them to segment 1. In effect, these broadcasts will keep flooding between the two segments, thus affecting all devices-because the NICs of these devices must handle all the broadcasts. As more and more devices generate ARP and other broadcast frames, the bandwidth will eventually be exhausted by these broadcasts. In this case, the network will crash, and the devices will run out of CPU cycles trying to process the broadcasts.As stated in Chapter 4, the NIC will only handle multicasts such that the device to which it belongs is running the application that is to receive the multicast: the application tells the NIC the address of the multicast it is to listen to and process. therefore, if the device is not running an application that uses the multicast, multicast flooding will not consume its CPU cycles. However, multicast will affect the bandwidth available per user because the switch floods the multicast; if the multicast is a high-speed video stream, the bandwidth will be exhausted quickly.MAC addresses are not properly learnedThe third problem posed by Layer 2 loops is that the switch cannot correctly learn the location of a device based on its MAC address. Returning to Figure 13.2, assume that PC-A's MAC address is 0000.01AA.AAAAPC-A generates an ARP request to learn PC-B's MAC address when Switch A and the switchSwitch B will both receive this ARP request and perform a learning function - associating PC-A's MAC address with Port 1. Next, they flood this frame to segment 2. Both switches will see this broadcast frame again and perform the learn function-associating PC-A to port 2, which causes both switches to assume that PC-A has moved from segment 1 to segment 2. Next, both switches flood this frame to segment 1, which in turn A moves from segment 2 back to segment 1. This flipping will be repeated as these two broadcast frames continue to cycle between the two segments.