High density AP environments & the benefit of tunneling

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If you're running or designing a centrally controlled WiFi solution involving high density AP placement, such as in a hotel or event center, you can significantly improve AP roaming speed and reduce wireless service interruptions to the end users by using GRE tunnels out to the access points.

I recently had an Wireless network implementation where we had very high AP density in a hotel. 146 APs spread over 5 floors and 265 rooms. We had an issue where a client could be connected to the network, with good signal and low noise, and as they moved around the building, they would sometimes lose internet connectivity for 5 minutes. Their WiFi connection would remain strong but their internet would drop. We messed around with roaming settings, signal strength, anything we could think of. We weren't making any progress. On each floor of the hotel there would be 3 or 4 switches for the APs (and other things) to connect to, giving us 15-20 total switches that all ran back to the network core (through a few intermediate switches). We started tracing ARP and MAC entries on the floor and core switches. We saw that when a client lost internet connectivity while roaming around the hotel that there would be disparate ARP and/or MAC entries on the AP switches, the intermediate switches, and the core. Once the "bad" MAC entry expired, the client would connect to the internet again.

Due to the AP density a roaming client could see anywhere from 3-10 APs at any one time. Those 10 APs might be connected to 10 different switches, connected to 3 different intermediate switches before reaching the core. As the client hopped rapidly between APs, the MAC and ARP refresh couldn't keep up, and so the client lost internet while maintaining excellent wireless network signal.

This particular implementation was running Ruckus H510 APs connected to the SmartZone 100 AP controller. We enabled GRE Tunnels and immediately saw the issue go away. A client could roam freely and never lose internet connection. Looking at the MAC and ARP tables, we saw the client traffic going directly to the SmartZone where it was encapsulated into the GRE tunnel and sent out to the AP.