only to the designated recipients, not to each person working on these floors. This avoids flooding each device with traffic for other nodes. In data communications parlance, a port is an interface into which a cable is plugged for linking a computer to another device (a laptop to a display), or to link devices to switches and networks. MAC Addresses in Layer 2 Switches Layer 2 switches send packets to devices based on their Media Access Control (MAC) address. Each device connected to a LAN has a MAC address. Layer 2 devices are considered Data Link equipment. They typically support up to 40Gbps speeds. If a port fails, the device connected to it loses its connection to the LAN. See Figure 2-1 for switches in wiring closets. This represents www.TechnicalPDF.com a single point of failure to the devices connected to them. If the switch crashes, all of the 16 to 24 devices connected to it are out of service. But the nodes connected to Layer 2 switches in other wiring closets don't lose service. Switches IIIII Backbone switch connecting devices on multiple floors with redundant fiber optical cabling to data centers and to other nodes*. IIII. Switch floor Backbone switches connect to other switches; not to Redundant fiber opfical cabing end-users' devices. www.TechnicalPDF.com Data center and to end-users' devices. Figure 2-1 A switch located in a wiring closet. Many Layer 2 switches are an industry-standard 19 inches wide for rack mounting and are typically housed in freestanding equipment racks with horizontally positioned blades. Circuit boards are often referred to as blades when they are dense, such as when they have many ports. Switches can be wall-mounted in wiring closets that don't contain other equipment. The Criticality of Layer 3 vs. Layer 2 Switches LAN backbones where core switches are located carry the highest volume of an organization's traffic. Backbone switches are more critical in supporting staff communications than switches in wiring closets. If a backbone switch fails, every Layer 2 switch plus t