Why can't I use IPv6 DNS?

[telometto]

For some odd reason, I cannot use DNS over IPv6.

Setup:

• Router has IPv6 enabled and receives IPv6 addresses; the option is currently set to 'SLAAC+Stateless DHCP
• Not using AdGuard with standalone Docker, but with k8s
• MetalLB
• Dual stack (IPv4/IPv6) is enabled in both k8s and metallb

Adding 2a10:50c0::ad1:ff to 'Upstream DNS servers' and clicking 'Test upstreams' shows a red toast in the bottom-right corner that reads "Server "2a10:50c0::ad1:ff": could not be used, please check that you've written it correctly".
Log excerpt:

...
2023/09/07 09:20:11.851074 1#46 [debug] bootstrap: connection to [2620:fe::10]:53 succeeded in 80.685µs
2023/09/07 09:20:11.851084 1#297 [debug] bootstrap: dialing [2620:fe::10]:53 (1/1)
2023/09/07 09:20:11.851092 1#302 [debug] bootstrap: dialing [2620:fe::fe:10]:53 (1/1)
2023/09/07 09:20:11.851132 1#201 [debug] bootstrap: dialing [2620:fe::fe:10]:53 (1/1)
2023/09/07 09:20:11.851202 1#224 [debug] bootstrap: dialing [2620:fe::fe:10]:53 (1/1)
2023/09/07 09:20:11.851226 1#45 [debug] bootstrap: connection to [2620:fe::10]:53 succeeded in 119.229µs
2023/09/07 09:20:11.851487 1#303 [debug] bootstrap: connection to [2620:fe::fe:10]:53 succeeded in 118.85µs
2023/09/07 09:20:11.852513 1#297 [debug] bootstrap: connection to [2620:fe::10]:53 succeeded in 103.544µs
2023/09/07 09:20:11.852595 1#224 [debug] bootstrap: connection to [2620:fe::fe:10]:53 succeeded in 88.824µs
2023/09/07 09:20:11.852431 1#302 [debug] bootstrap: connection to [2620:fe::fe:10]:53 succeeded in 69.804µs
2023/09/07 09:20:11.852619 1#201 [debug] bootstrap: connection to [2620:fe::fe:10]:53 succeeded in 80.539µs
2023/09/07 09:20:21.850774 1#117 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:49711->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.850879 1#309 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:45268->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.850843 1#204 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:48832->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.851116 1#118 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:37002->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.850891 1#296 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:47900->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.851389 1#199 [debug] parallel lookup: lookup for family.adguard-dns.com failed in 20.004734237s: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:49711->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.850922 1#295 [debug] [2a10:50c0::ad1:ff]:53: response received over udp: exchanging with [2a10:50c0::ad1:ff]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:47325->[2a10:50c0::ad1:ff]:53: i/o timeout
2023/09/07 09:20:21.850993 1#308 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:46586->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.851603 1#323 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:52554->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.851642 1#324 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:49917->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.851743 1#160 [debug] parallel lookup: lookup for family.adguard-dns.com failed in 20.004727114s: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:45268->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.851884 1#322 [debug] parallel lookup: lookup for family.cloudflare-dns.com failed in 20.002440502s: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:52554->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.851929 1#202 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:50180->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.851981 1#307 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:45235->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.851995 1#268 [debug] finished POST 10.0.0.10 /control/test_upstream_dns in 20.009249786s
2023/09/07 09:20:21.852188 1#223 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:41132->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.852064 1#203 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:41237->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.852334 1#46 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:46031->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.852407 1#300 [debug] parallel lookup: lookup for family.cloudflare-dns.com failed in 20.004235265s: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:48832->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.852454 1#306 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:48784->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.852568 1#305 [debug] parallel lookup: lookup for family.adguard-dns.com failed in 20.006352241s: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:45235->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.852609 1#303 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:57760->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.852717 1#45 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:45861->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.852778 1#297 [debug] [2620:fe::10]:53: response received over udp: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:38410->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.852840 1#321 [debug] parallel lookup: lookup for family.cloudflare-dns.com failed in 20.003433816s: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:46031->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.852889 1#224 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:51960->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.852997 1#302 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:43122->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.852923 1#221 [debug] parallel lookup: lookup for family.adguard-dns.com failed in 20.00865535s: exchanging with [2620:fe::10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:47900->[2620:fe::10]:53: i/o timeout
2023/09/07 09:20:21.853114 1#201 [debug] [2620:fe::fe:10]:53: response received over udp: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:53773->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.853061 1#222 [debug] parallel lookup: lookup for family.adguard-dns.com failed in 20.00884704s: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:41132->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.853221 1#200 [debug] parallel lookup: lookup for family.adguard-dns.com failed in 20.007474099s: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:50180->[2620:fe::fe:10]:53: i/o timeout
2023/09/07 09:20:21.853114 1#301 [debug] parallel lookup: lookup for family.cloudflare-dns.com failed in 20.006206164s: exchanging with [2620:fe::fe:10]:53 over udp: read udp [fd02::d56:6aff:8292:f252]:57760->[2620:fe::fe:10]:53: i/o timeout

Output of kubectl get svc -n adguard:

NAME              TYPE           CLUSTER-IP      EXTERNAL-IP                      PORT(S)                                                                                                                                                                                            AGE
adguard-service   LoadBalancer   10.152.183.66   10.0.0.10,fe80::8a51:f645:4d98:8ed5:a   3000:32761/TCP,80:30511/TCP,53:31641/UDP,53:31641/TCP,67:31024/UDP,68:30638/TCP,68:30638/UDP,443:31506/TCP,443:31506/UDP,784:30844/UDP,853:31729/TCP,853:31729/UDP,5443:31014/TCP,5443:31014/UDP   14m

This is the current DNS page:


NOTE: The first IP, which is not easily discernible, under 'Bootstrap DNS servers' is 9.9.9.10.

To be honest, I'm not really sure what's wrong. I seem to have configured everything as it should be, but I cannot seem to get IPv6 to work. Or, at least, not getting IPv6 DNS to work.

[ainar-g]

IPv6 upstreams work for me, including 2a10:50c0::ad1:ff. Please make sure that those IPv6 are actually available from the device and/or container using something like dig or nslookup. There are quite a few instances where either the providers block IPv6 DNS traffic or the IPv6 network settings are misconfigured.

[telometto]

Thank you for your reply. This is the output from within the pod:

$ kubectl exec -it adguard-deployment-5b6b759d5d-rdz8n -n adguard -- /bin/sh
/opt/adguardhome/work # nslookup 2a10:50c0::ad1:ff
Server:		10.0.0.10
Address:	10.0.0.10:53

Non-authoritative answer:
f.f.0.0.1.d.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.c.0.5.0.1.a.2.ip6.arpa	name = dns.adguard.com

/opt/adguardhome/work # nslookup 94.140.14.14
Server:		10.0.0.10
Address:	10.0.0.10:53

Non-authoritative answer:
14.14.140.94.in-addr.arpa	name = dns.adguard.com

[telometto]

Also, here's the output from my physical server:

$ nslookup 2a10:50c0::ad1:ff
f.f.0.0.1.d.a.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.c.0.5.0.1.a.2.ip6.arpa	name = dns.adguard.com.

Authoritative answers can be found from:

[ainar-g]

@telometto, that is not the correct use of nslookup, I'm afraid. You are asking it to resolve the rDNS query for the IP address, not query the IP address itself. The correct way is:

nslookup -debug 'www.example.com' '2a10:50c0::ad1:ff'

The first argument is the hostname or IP address to resolve. The second is the server to use.