ess exists on one network, while the real servers exist on one or more others. Pros: Expandability. Routed models allow for the real servers to be geographically diverse. The possibilities here are almost limitless. Easier to understand for people used to layer-3 environments. No spanning-tree issues. Cons: Layer-3 load balancing can be costly. The CSM-S module for the 6500 switch is one of the most expensive modules Cisco produces. Requires network design and additional IP address space to implement. Because the real servers must be on a different broadcast domain from the virtual server, a routed load balancer cannot be dropped into an existing flat network without redesigning the network. Load balancing in the Cisco world can be accomplished in one of the following ways: IOS IP server load balancing Load balancing in IOS is a very easy way to get started. The commands are very easy to understand, and they are very similar to those used with CSMs. Should you ever decide to upgrade, the transition will be smoother than with other methods such as Local Directors. The downside of IOS load balancing is that it can be CPU-intensive. If you're balancing more than a few servers, or if you find yourself building multiple virtual servers, it's time to upgrade to dedicated hard- ware. IOS SLB requires an SLB-capable version of IOS. Local Directors I hesitate to include Local Directors because they are end-of-sale as of this writ- ing (they are supported until 2008). It's a shame that Cisco has discontinued them, because they were an excellent product. The Cisco Local Director is very easy to configure and manage. Its only shortcoming is that it must be deployed as a bridge. This not only makes it far less useful in complex environments (no doubt the cause of its demise), but also makes it a touch harder to understand for those engineers who live in a layer-3-only world. Types of Load Balancing Content Switches Either as standalone units or in the excellent CSMs for the 6500-series switch, the Content Switch is the top do