 line is now the cutting edge of the Cisco data-center class of switches. For more information on switch types, refer to Chapter 2. Cisco 6500- series switches are discussed in more detail in Chapter 17, and the 3750 is the focus of Chapter 19. Chapter 18, which covers Nexus switches, is also included for your reading pleasure. Chapter 16: Multilayer Switches A quick word is in order about choosing the right device for the job. Many of my clients buy what I call closet switches for use in their data centers. A great example of this is the Cisco 3750. This is a very attractive switch because it can be stacked, allowing for pretty decent port densities. You must be careful, though, as this model switch is really designed for end-user connectivity. Sure, the purpose of the switch is to forward pack- ets, and the switch doesn't care what's connected to it, but the 3750 has only one power supply. This can be mitigated with Redundant Power System (RPS) add-ons and mul- tichassis EtherChannel, but the RPS is an add-on device that consumes a rack unit. Consider, also, that the 3750 only supports 127 spanning tree instances. With the default installation of RPVST, you will not be able to add a 128th VLAN and have spanning tree protect you from loops. Trust me when I tell you that this is not a fun situation in which to find yourself. Cisco has switches to support the higher availability demands found in the data center. Switches like the 4900 series come with dual power supplies and are designed for top- of-rack installations. The Nexus line is designed specifically for data centers and in- cludes proper front-to-back airflow along with dual power supplies. Nexus 5000 and 5500 switches allow you to add FEXs for port densities exceeding the 6509, but some models don't support Layer 3. Where possible, try to avoid using the wrong switch to save a few bucks. You'll just end up paying someone like me in a few years to get you out of the corner you've painted yourself into. Believe me, paying for the better switch is cheaper. 