How do I reset DHCP address allocation on my iPhone 6? I need to briefly connect several hundred devices to the iPhone 6 Hotspot to test their Wi-Fi functionality.  I only need to connect 3 or 4 at a time, and each is only connected for a few minutes.  After checking about 12, no more devices would connect to the phone.  If I power any of the first few back up, they connect to the phone just fine.  If I try to connect any of the later devices to a new Wi-Fi source, it works just fine.

It really seems like the iPhone has run out of IP addresses to allocate to new devices.

Is there any way to reset the allocation so it will reuse addresses it has used recently?
You might also try Settings -> General -> reset -> reset network Settings

I believe that will flush DNS and DHCP and should have the desired effect. 

Note that you will also have to re-enter any WiFi passwords that were previously saved.