Wanted to say thank you for this post, I was struggling to figure out why our new android devices suddenly couldn't load facebook on wifi, and it was draining our batteries trying.
I set it to "none" and off I went. Now I will go back and set up IPv6 locally since my ISP does support IPv6 (I have it getting an address on the WAN side, so I'll setup IPv6 on the LAN).
Thanks again!