 of ports, remember that the backplane speed of a stack is limited to 32 Gbps. Chapter 2: Hubs and Switches Flexibility The Cisco 6500 chassis will accept modules that provide services outside the range of a normal switch. Such modules include: Firewall Services Modules (FWSMs) Intrusion Detection System Modules (IDSMs) Application Control Engines (ACE) modules Network Analysis Modules (NAMs) WAN modules (FlexWAN) Redundancy Some fixed-configuration switches support a power distribution unit, which can provide some power redundancy at additional cost. However, Cisco's chassis- based switches all support multiple power supplies (older 4000 chassis switches actually required three power supplies for redundancy and even more to support VoIP). Most chassis-based switches support dual supervisors as well. Speed The Cisco 6500 chassis employing Supervisor-720 (Sup-720) processors supports up to 720 Gbps of throughput on the backplane. The fastest backplane in a fixed- configuration switch-the Cisco 4948-supports only 48 Gbps. The 4948 switch is designed to be placed at the top of a rack in order to support the devices in the rack. Due to the specialized nature of this switch, it cannot be stacked and is there- fore limited to 48 ports. Chassis-based switches do have some disadvantages. They can be very heavy, take up a lot of room, and require a lot of power. If you need the power and flexibility offered by a chassis-based switch, however, the disadvantages are usually just considered part of the cost of doing business. Cisco's two primary chassis-based Catalyst switches are the 4500 series and the 6500 series. There is an 8500 series as well, but these switches are rarely seen in corporate environments. The Nexus switches can fit in either camp depending on the model. The Nexus 7000 chassis switch is available in a 10-slot or 18-slot chassis. These models have all the benefits and drawbacks of any other chassis switch, though as of this writing the 7000 does not support many service modules. Word on the street is that