ccna r&s cisco commands list

ccna r&s cisco commands list.. Destination address is an unknown unicast address: the destination MAC address is not included in the CAM table. The bridge and switch make switching decisions based on the destination MAC address.Unicast framesWhen using unicast, the source device sends a different copy of the frame to each destination device.' For example, if the device needs to send the same information to 50 different target devices, it creates 50 frames with different destination MAC addresses. Upon receiving a frame whose destination address is a unicast address, the switch looks up the address in the CAM table to make a forwarding decision. If this address is not contained in the CAM table, the switch floods the frame out of all ports. If the address is found in the CAM table, the switch will forward the frame out of only one port (the port corresponding to the destination address).The discussion of the forwarding process here is directed at transparent switches, and it is important to keep this in mind. Therefore, if the switch does not know where the target device is (obviously, the source device believes that the target device is in the same logical segment as it), it must flood the frame to ensure that it will receive the frame as long as the target device is in the current broadcast domain. Flooding is not required for every forwarding. If the target device receives the frame, it may send a response frame to the source device. Through the learning process, the switch now knows the location of the target device, so for subsequent frames sent by the source device to or returned from the target device, they will be intelligently forwarded rather than flooded.One problem with this process is that if the CAM table is full, the switch will not be able to add new entries to it, so for traffic going to a destination address that cannot be added to the CAM table, the switch always floods. With this in mind, it is critical that the switch purchased stores the MAC addresses of all devices in the current switched network. If your switched network has 2000 devices, but the switch's CAM table can only store 1000 entries, this will cause problems. In this case, the switch will flood the traffic going to half of the target devices, causing serious bandwidth and performance problems for the network.Broadcast and Multicast FramesA broadcast is a frame that is sent to all devices in the broadcast domain. For example, if a device needs to send the same information to 50 different destination devices, it can create only one frame with a destination MAC address of FFFF.FFFF.FFFF, so that all the destination devices will process it. A switched network can be thought of as a logical bus where all devices are located on the same cable. Therefore, when the switch receives a broadcast, it needs to ensure that all devices will receive it, so the switch floods this frame to ensure that all devices will receive it.A multicast is a frame that is sent to a group of devices, and a multicast group contains devices that want to receive multicast data. A multicast group may not contain any devices, and may also contain all or some of the devices in the broadcast domain. In a standard switch configuration, the switch receives a multicast frame and floods it out of all ports. Only devices that have joined the appropriate multicast group actually process the multicast frames, while all other devices discard them. The problem with using unicast for certain types of information is that it can negatively impact network performance. For example, suppose you have a network and want 10 of the devices in it to receive a specific multimedia stream, such as live video. One solution is to have the video server send 10 copies of this information to each target device using unicast. Obviously,if this multimedia stream has a traffic volume of 5 Mbit/s,the server will generate 50 Mbit/s of traffic.Exam Essentials Bridges and switches always flood the following three types of frames: multicast, broadcast, and unicast with an unknown destination address CAnother solution is to use broadcasts. In this case, the video server will generate only one stream of information. The problem with this approach is twofold. First, the switched infrastructure will flood this traffic to every device (including the 10 devices that want to receive them), thus wasting a large amount of bandwidth. Second, since the destination address of broadcast frames is FF:FF:FF:FF:FF:FF:FF,each