Can the Nexus 6P use GSM data if the connected Wifi has no route to the internet? I have a Nexus 6P and use it to connect to a Phantom 3 4K drone using WiFi. Obviously, because it's a private WiFi network with no external connectivity my phone can not contact the internet via WiFi.

This wouldn't be a problem but the app that I need to use, DroneDeploy, requires a connection to the drone via the DJI Go app (which needs to use the WiFi to connect) and the internet to pull down waypoint settings and to use mapping images.

I have a 4G connection however when my phone connects to the WiFi it doesn't seem to try and fall back on the GSM for external connectivity.

Is there a way I can get my phone to use the 4G connection for the internet connection while maintaining the private WiFi link to the drone?

Thanks in advance!
Android 5+ should do this automatically in most cases if there is no route to the internet you will see ! next to wifi icon in notification tray.  You should also still see the mobile data icon showing you are connected to mobile data like LTE or 4G.

You could try to go in to developer settings and enable Cellular Data Always Active

Enabling Developer Settings Menu in Android 6 (4-7 I believe)


Go in to device settings
scroll to bottom
Tap About Phone or About Device or About Tablet
Scroll down to where it says Build Number
Tap this about 8-10x (You will see toast come up after the first several taps and it will say you are x taps away from enabling development settings).


When you are done you can hit back until you are back to the Device Settings window.  Now you should see a new entry toward the bottom labeled Developer Options {}

Enabling Cellular Data Always Active [and possibly Aggressive Wi-Fi to Cellular Handover]


Go in to Device Settings Menu
Tap Developer Options
Scroll Down to Cellular Data Always Active
Tap to Enable this
As it says it will keep Mobile Data connected even if Wi-Fi is connected (so when you disable Wi-Fi Mobile Data is already there no wait.  This can cause your battery to drain more quickly (mine isn't hardly noticeable and I have this enabled and have for some time), but if battery life is a concern it is something to keep an eye on until you have used it and know how your device reacts.
You could also try enabling Aggressive Wi-Fi to Cellular Handover at the same time as this tells the device to favor cellular data when Wi-Fi Signal is low, BUT if drone signal gets low while flying Wi-Fi may drop in favor of Cellular so you may want to try this when drone is flying in safe conditions.  This is just something that could help you in your endeavor it is not a mandatory setting if you rather leave it disabled and only try it if you don't get what you want in your first tests.


Caveat with some Basic Info

You MAY still have some issues since you will now be connected to both networks. You won't know without testing if for instance I go to a website it first sends out a DNS request. The device will have to choose whether to use Wi-Fi or Cellular Data for this request which is hard to adjust [Google: Split DNS VPN to get a feel for what I mean here].  You can get all nitty gritty and look at modifying the routing table if you have root access and all, but hopefully it just works and enabling this setting is all you need.

Note About Accessing Dev Settings

Some Android Versions maybe slightly different in ow you "unhide" developer settings.  So, if what I detailed does not work you can Google: Android x.x Enable Developer Settings (replace X.X with your android version ie. Android 4 or Android 4.4.1 depending on what exact version you are running).