I am having issues with the iPhone 7 and 7+. I believe the issue is entirely client side, but I'm still the one needing to fix it. We have an 802.1x certifcate based SSID, and periodically throughout the day iPhone 7's will stop working. The iPhone will show connected, but it not longer shows up in ZoneDirector. Obviously data stops transmitting as well. The only happens after it has been idle for a few hours with user activity.
This only happens on the new iPhone 7's and 7+'s. I have not been able to recreate it on any other IOS device, even with the same version. As I do not have one to test with I don't believe I would have much luck trying to submit a ticket. Any ideas?
As a follow up to this statement, we eventually discovered that our specific issue was related to NAT behaviour. We run a Cisco ASR with a NAT pool for SNATing the clients out to the internet. We ran into some other issues on the ASR relating to address+port exhaustion which lead to a code upgrade. What was noticed after the code upgrade was the NAT behavior changed, specifically with how it assigned outer source ports. Before the code upgrade, all source ports were randomized on the outside interface. After the code upgrade, all source ports were maintained unless there was a conflict, then a randomized source port was used for outgoing sessions. I believe this change in behaviour made it easier for the iPhones to maintain data paths to messaging services. Suddenly they all stayed connected while the screens were off, the difference was night and day after the NAT code upgrade.
There's a lot of buzz in online forums about iPhones disconnecting from some consumer grade WiFi gear and staying connected to others. I recommend calling Apple customer service number for more help. My gut tells me this could have something to do with the way that 802.11 power management is implemented on different vendors.