IPv6 DNS timeouts & slow name resolution with DoH (DNS over HTTPS) on Slate AX

I’m testing out DoH on the new Slate AX I got for Christmas and using the IPv6 host at my preferred provider seems to reliably result in slow name lookup and occasional timeouts. I am not using Adguard Home, rather I’ve set this up in the “DNS” section of Network settings in the GLi firmware. Edit: I’m also using OpenVPN.

When I enabled DoH I added two entries from the built-in server list, namely quad9-doh-ip4-port443-filter-pri and quad9-doh-ip6-port443-filter-pri

After a while I noticed that all name lookups were laggy and sometimes failing. Quad9 has always performed well for me when I use their normal DNS service on IPv4, and they have a POP near where my VPN terminates.

I eventually found that removing the IPv6 server from the list in the GLi DNS settings eliminates the problem. Not sure if this is a bug or not, but I figured I’d make a post either way - if it’s a bug then I’ve reported it, if it’s undocumented behavior then the post will exist for people searching on the forum.

Happy 2023 everyone.

Thank you for your feedback. VPN does not support IPv6 yet.