Netgear EX6400 WIFI Extender - if you have this problem don't waste your time trying to fix it; there apparently is no solution.
When it is working properly this product offers outstanding performance. Unfortunately, after 10 days of trial and error, 5 calls to and hours on the phone with Netgear Tech Support (India), and returning and replacing the first device with a new one, I could not get the EX6400 to work for even one day without having to reboot it. While it was easy to set up and connect to my Netgear 6250 dual band router, and position in a location with a strong wifi signal, it would stay connected to the router, but all attached devices on the extender would show a “NO INTERNET CONNECTION” message with an ! through the wifi symbol after working for a while. The router and all devices connected directly to it would still have an internet connection. The only solution is to reboot the extender (not the router). Sometimes the problem would occur within minutes, sometimes hours. Unfortunately when the internet connection is lost, because the wifi is still connected the iPhone/iPad would automatically revert to using cellular data while attempting to connect to the internet even if standing next to the extender. The devices would not revert to the weaker router signal which still had an internet connection. Very frustrating.
Netgear support at first tried to convince me there was signal interference from a microwave oven or cordless telephone. The router and extender have been updated to the latest firmware. So they had me move the extender to a position that was 25’ away from any possible source of interference. Then I changed the signal channels on the router. Neither solved the problem so they said it was a bad device that should be returned and replaced under warranty. The replacement, which I got from a different source to be sure I got one from a different batch had the same problem.
SOLUTION: I returned the second EX6400 and exchanged it for a Netgear Nighthawk EX7000, which was only $8 more at Best Buy and provides slightly better performance and, so far after 2 days, appears stable not requiring rebooting to continue to operate properly. I don’t need 5 ethernet ports and would prefer not to have it taking up space on my credenza with its external antennae but so far it is doing its job well.