Q: My wireless LAN vendor says that I need to deploy a wireless controller to manage my access points. Should I? 

A: Personally, I think that if you have more than four or five APs, investing in a wireless LAN (WLAN) controller is worth the cost, just from a management and maintenance perspective. The big advantage of installing a wireless controller is that it lets you centrally configure and control your access points (APs). If you need to deploy many APs, this ability can save you a lot of time. Let me give you an example.

The other day, I was bringing a new AP online without a wireless controller. The first thing I did was to assign the AP an IP address. To do so, I established a Telnet serial connection into the AP through the console port and configured the CLI to give the AP a static IP address. Next, I connected to the AP with an Ethernet cable and brought up the web GUI. I then went through the express setup to configure the AP parameters. I used the wireless interface to turn on the radios and used the network interface to turn on SNMP so that I could centrally manage the AP. The entire process took me approximately 90 minutes although I was quicker with the next AP)!

The primary advantage of a wireless controller is that you just plug the AP into the controller, which then automatically finds and configures the AP. If you want to make changes—for example, change the quality of service (QoS) parameters—to all your APs, you can do so centrally instead of reconfiguring each AP individually. Wireless controllers have other advantages, in terms of security and the ability to roam across subnets.

Like network switches and routers, WLAN controllers come in a range of sizes, formats, and licensing options, depending on whether you're deploying your WLAN at a small, midsized, or large site. For example, Cisco 2500 Series Wireless Controllers are small standalone controllers that support 5 to 50 APs. The popular Cisco 5500 Series Wireless Controllers manage 12 to 500 APs. And Cisco Flex 7500 Series Wireless Controllers centrally manage APs at remote branch locations and scale to as many as 3,000 APs.