ccna 200 301 bookstore chains long in decline

ccna 200 301 bookstore chains long in decline.When a filter table is constructed on a Layer 2 device, it forwards only those data frames for which the destination hardware address is already located. If the destination device is on the same network segment as the frame, the Layer 2 device locks the frame to prevent it from going to another network segment. If the destination is located in another segment, the data frame can only be transmitted to that segment. This is called TransparentBridging.If a switch interface receives a data frame and does not find the frame's destination hardware address in its filter table, it forwards the frame to all segments to which it is connected. If the unknown device to which the "mystery data frame" is destined answers the forwarding action, the switch updates the filter table with the location of this device. However, because the destination address used to transmit the frame is a broadcast address, the switch forwards the broadcast to all connected segments by default.All devices that receive this forwarded broadcast belong to the same broadcast domain. This creates a problem: Layer 2 devices can generate Layer 2 broadcast storms and eventually affect device performance; the only way to stop the spread of broadcast storms is to use a Layer 3 device, a router.The biggest benefit of using a switch instead of a hub in an interconnected network is that each port of the switch is effectively a conflict domain itself (whereas a hub creates a large conflict domain). But even with a switch, by default, you still can't separate broadcast domains. Neither switches nor hubs can separate broadcast domains. They will simply forward all broadcasts.Another advantage of using LAN switching technology instead of hubs is that every device plugged into the switch can transmit data at the same time one-at the very least they can think that only one host is plugged into each port, not a hub. As you may have guessed from reading this, hubs only allow one device in the same network segment to send data at the same time.2.3.7 The Physical LayerFinally we get to the bottom layer, the PhysicalLayer does two things: sends bits and receives bits. Bits are made up of 1's and 0's - Morse encoding expressed as numbers. The physical layer communicates directly with various types of actual communication media. Different types of media will represent these bits in different ways. Some use multiple audio, others use state changes - voltage from high to low, or low to high. For each type of medium, . Each requires the use of a specific protocol to describe the correct bit format, the way to encode data into the medium signaling, and the different qualities of the physical medium connection interface.The physical layer defines all the electrical characteristics, mechanical characteristics, procedural requirements, and functional requirements needed to activate, maintain, and close the physical link between two end systems. This layer is also responsible for distinguishing between DTE (data terminal equipment) and DCE (data communications equipment) interfaces (some old telephone company employees still refer to DCE as data electrical1.5 Summary 49circuit termination equipment). The DCE is usually located at the carrier and the DTE is the device connected to it. A modem or CSU/DSU (Channel Service Unit/Data Service Unit) is usually required to obtain the services provided by the DTE.