Interesting Look at DoH3/QUIC possible configurations

For the purpose of this post, I’ll only go over DoH3 since it’s similar to DoH and easier to configure for yourself to test.

So I messed around with the link naming system on Adguard iOS and I found some interesting stuff. There’s been an old previous post about setting DoH3 and trying odd dns setups like steering.dns.nextdns.io and so on, but there’s no talk about what’s pretty interestingly possible.
 

With the proper DoH3 addressing you can get something gnarly like h3://dns.nextdns.io typically BUT you can expand it even more with specific connections you’d prefer making. There was a post like this for DoH but it never went over how you can do this for DoH3 or combine more than one option at a time too.

To set up a specific connection preference, you can set h3://ipv6-anycast.dns.nextdns.io and you’ll have DoH3 set to ipv6 primarily and enable anycast. You can add 1 or 2 on dns (dns1) to pick an anycast server. Same with ultralow (h3://ipv6-ultralow.dns.nextdns.io). 
 

What seems very interesting though broken is the option which doesn’t seem to cause any errors is h3://ipv6-only.dns.nextdns.io. 
 

Keep in mind this is all possible with normal DoH profiles too. I haven’t tested it but it should be possible with dashes on the other DoH3 link (https://doh3.dns.nextdns.io) if you add what you want before or after doh3 (doh3-ipv6).
 

These secret configurations are pretty interesting, and pretty helpful if someone checks their ping.nextdns.io and consistently find a specific server’s got a better connection than the one they’re connected to. For myself I genuinely wonder if it’s possible to force IPv6 as the sole primary connection. Interesting stuff, hope more people could test stuff out here.