 this will change as the product line evolves. The Nexus 5000, having only one (5010) or two (5020) expansion modules can be expanded through the use of fabric extenders (FEXs). FEXs appear to be physical switches, but are actually more like a module connected to the 5000s. The Nexus 2000 switches act as FEXs. With the capability to connect up to twelve 48-port FEXs to a single (or pair of) Nexus 5000s, each Nexus 5000 behaves more like a 12-slot chassis than a fixed-configuration switch. The Nexus hardware chapter will go into more detail regarding Nexus expandability. Switches Planning a Chassis-Based Switch Installation Installing chassis-based switches requires more planning than installing smaller switches. There are many elements to consider when configuring a chassis switch. You must choose the modules (sometimes called blades) you will use and then determine what size power supplies you need. You must decide whether your chassis will use AC or DC power and what amperage the power supplies will require. Chassis-based switches are large and heavy, SO you must ensure that there is adequate rack space. Here are some of the things you need to think about when planning a chassis-based switch installation. Rack space Chassis switches can be quite large. The 6513 switch occupies 19 RU of space. The NEBS version of the 6509 takes up 21 RU. The 10-slot Nexus 7010 consumes 21 RU as well, while the 18-slot model 7018 requires 25 RU. A seven-foot telecom rack is 40 RU, SO these larger switches use up a significant portion of the available space. Be careful when planning rack space for Nexus switches. The Nexus 5000 series is as deep as a rack-mount server and requires the full depth of a cabinet for mounting. The Nexus 5000 switches cannot be mounted in a standard two-post telecom rack. The larger chassis switches are very heavy and should be installed near the bottom of the rack whenever possible. Smaller chassis switches (such as the 4506, which takes up only 10 RU) can be mounted higher in the rack. Always use a mi