Cisco Enterprise Infrastructure Access Points
When working with Access Points (APs) in Cisco’s enterprise infrastructure, you will encounter two modes of access points: Autonomous mode and Lightweight mode. If you use hardware from other vendors, their names may be different, but the function and operation will be similar.
When 802.11 networking began, all APs were Autonomous mode, which means that each AP worked as a standalone unit with no knowledge of or interaction among other APs. Autonomous mode was fine in the beginning when wireless networking was often limited to providing network access in common areas or boardrooms, and continuous roaming was not a requirement.
Wireless networks tend to grow, and that means a typical network might deploy from one to ten access points across the network environment, and an environment of that size is still easily managed with Autonomous mode APs. Although these APs are connected to the same network, and may use the same SSID, they are all individually configured and separate from one another.
In most small networks, wireless still starts out as an idea to make life a little easier in conference rooms and boardrooms, so these networks tend to start with just one AP in those locations. If you are deploying only one AP on your network, then in all cases you will choose to deploy an Autonomous mode AP.
Unfortunately, after that first AP is deployed and users become used to the flexibility and functionality it offers, you will undoubtedly receive a request for another one.
If you are planning to deploy four or more APs on a new network, you should give thought to Lightweight mode APs because you will be close to the breakeven point in cost between purchasing autonomous APs, and going forward beyond that, you will have an easier infrastructure to manage using Lightweight mode APs.
Rather than using Autonomous mode APs, you can use Lightweight mode APs if you have a network component that offers Wireless LAN Controller services. Cisco offers the Lightweight mode option on most of its APs, so you can purchase them with either a controller-based IOS software image (using Lightweight Access Point Protocol, or LWAPP) or a standalone IOS software image.
A sample of how the controller and APs fits together in your network is shown. Some Wireless LAN Controllers have Power over Ethernet (POE) ports that allow you to connect APs to; you can also connect the AP to any other POE switch on your network. It does not matter where the AP is on your network, it will still get all of its management information from the Wireless LAN Controller.
To have Wireless LAN Controller (WLC) services on your network (which is the management device that manages your LWAPP devices), you can use any of the following:
Cisco 2100 series controller
Cisco 4400 series controller
Catalyst 6500 series Wireless Services Module (WiSM)
Cisco 7600 series Router Wireless Services Module (WiSM)
Cisco 28/37/38xx series Integrated Services Router with Controller Network Module
Catalyst 3750G Integrated Wireless LAN Controller Switch
In this scenario, the access points all have their configuration managed by the WLC. You can set a single policy on that WLC, and that configuration setting can be deployed to all managed access points, reducing the workload of managing hundreds of lightweight access points (when using the Cisco 7600 series Router Wireless Services Module).
Also, in this configuration, some of the processing work that would normally be done at the AP can be offloaded to the WLC, leaving more CPU cycles available on the AP.
As mentioned earlier, if you are deploying four or more APs, you should get a quote on a solution that includes lightweight APs and a WLC because the price will likely be similar to the solution with autonomous APs.
If you already have Autonomous mode APs, you can convert them to lightweight to blend them into your new managed network, or you can deploy them elsewhere in your organization where lightweight APs will not fit the requirements.
Places that cannot use LWAPPs are locations that do not have direct and permanent network connectivity to the WLC, such as isolated segments of your network that have only periodic connections to where the WLC resides. Many of my clients run networks on ships or ocean platforms where there they would require autonomous APs.