Hi - I use a 4g phone as a backup connection on my Vigors using WAN2. This is working fine with a 2860n, and pc's can tether direct to the smartphone no problem...but with the 2860ac the WAN2 simply does not come up despite the configuration being the same as on the 2860n! Both have the latest firmware applied - I thought the 2860ac had been working previously (before the latest firmware) but haven't checked for a few months so can't be certain.
Any thoughts?

I have some thoughts but I doubt that they will help - I do the same as you with a 2926ac and an Android phone. The WAN2 connection has a mind of its own - it will stay up for many hours, then drop and come back on at some later time. The connections/disconnections appear to be random. The router and phone are about 5 feet apart. Very annoying.

Yes this is with an android phone also, but just wont connect at all. Anything in your settings that you think I should check out? Thanks.

Can you configure both units to log to a SYSLOGrd server? (I'm not convinced the built-in thing works anything like as well...).

You may be able to compare-and-contrast the two, to spot the difference.

Inbound Wifi connections appear on the "User Access" tab, but it may be on the "WAN" tab in your case.

I can force the WAN2 connection to re-establish by disabling 5GHz wifi (that's the band I'm using) and then re-enabling it. I've set the syslog server to my NAS so I'll see what transpires...

Thanks will check out disabling ac - after all that is the difference between the routers!! Thanks.