My wife gets confused by this wireless lan vs internet access thing when things go wrong.
Unfortunately apple devices stick with wireless lan even when the internet connection from the router via the main pipe, dsl say, has gone down, and they should switch to 4G if only they knew and had the clue. I wish there was an implementation of a system using a suitable protocol available to link routers to iOS boxes and control routing, there are of course several routing protocol candidates.
Because when the internet access link goes down the seductive wireless lan still keeps the iOS boxes faithful to wireless I have now got 3G failover going in the router. (Have failed to work out how to set 4G NIC up.) this means that wireless lans are not so evil, luring iOS devices when those devices should switch to 4G.
(I don’t know if ther’s Any way if telling devices to switch default gateway?)