If you have a healthy budget to set up a new data center, the Nexus is indeed the way to go, advises Kerravala. But if you have a Catalyst installed base, then it may be prudent to stick with the Cat. Certainly a sea of network administrators are already familiar with Catalyst's IOS (Internetwork Operating System), a cryptic but ultimately very powerful operating system. With the use of scripts, IOS offers "so much flexibility, there was almost no problem you couldn't solve," Kerravala says.
Independent channel vendor NHR (Network Hardware Resale) tends to default to pitching the Catalyst for most of its customers. "There is a lot of aggregation switching out there that the 6500 is perfect for," says Michael Lodato, NHR senior vice president of sales and marketing.
While praising the Nexus' muscle, Lodato cautions, "If you don't need the Nexus, don't buy the Nexus," he says. "Not all of us are low-latency traders sending traffic from Chicago to New York. A lot of us are just sending email around the office."
Key to picking which switch to deploy is "understanding how it will be used," Vargas says. Many seemingly small factors, such as the operating environment, may influence a decision, he says. Nexus requires a deeper rack than Catalyst, and may require a different form of airflow patterns to keep cool. It also requires a different power supply.
Each switch has a considerable number of features the other doesn't. The Catalyst has a broader feature set, while the Nexus focuses on the high-level cutting edge features such as Layer 2 encryption - a tasty treat for those low-latency traders - and the ability to set up virtual switches.
Vargas had one customer who was all set to purchase the Nexus (pictured below), until he asked if the client uses some form of application acceleration, such as a Riverbed appliance. The customer indeed had one, but it used a version of the Web Cache Communication Protocol (WCCP) that the Nexus did not support. So a Cat was deployed instead.
Vargas advises customers to clear space on a white board and list all their requirements, and then check which features each switch supports. "Once you're done with that, you get a pretty definitive answer," he says.