As per title, if I were to set my ethernet connection to use my router’s DNS (192.168.100.1), there would be no incoming internet, but I can access my router.
If I change the DNS4 to Google’s DNS, 8.8.8.8, it works.
$ nslookup example.org fe80::1
;; UDP setup with fe80::1#53(fe80::1) for example.org failed: invalid file.
;; UDP setup with fe80::1#53(fe80::1) for example.org failed: invalid file.
;; UDP setup with fe80::1#53(fe80::1) for example.org failed: invalid file.
$ resolvectl query example.org example.org: resolve call failed: Could not resolve ‘example.org’, server or network returned error REFUSED
$ resolvectl status --no-pager
Global
Protocols: LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub
Link 2 (enp38s0)
Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
Protocols: +DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: fe80::1
DNS Servers: fe80::1
Link 3 (wlo1)
Current Scopes: none
Protocols: -DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
Link 4 (wlp42s0f3u2u3)
Current Scopes: none
Protocols: -DefaultRoute LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
$ systemctl status systemd-resolved.service
● systemd-resolved.service - Network Name Resolution
Loaded: loaded (/usr/lib/systemd/system/systemd-resolved.service; enabled; preset: enabled)
Drop-In: /usr/lib/systemd/system/service.d
└─10-timeout-abort.conf
Active: active (running) since Thu 2023-04-20 23:49:17 +08; 7min ago
Docs: man:systemd-resolved.service(8)
man:org.freedesktop.resolve1(5) writing-network-configuration-managers writing-resolver-clients
Main PID: 1658 (systemd-resolve)
Status: “Processing requests…”
Tasks: 1 (limit: 77001)
Memory: 6.3M
CPU: 138ms
CGroup: /system.slice/systemd-resolved.service
└─1658 /usr/lib/systemd/systemd-resolved
Apr 20 23:49:17 x570-fedora-amac systemd-resolved[1658]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc>
Apr 20 23:49:17 x570-fedora-amac systemd-resolved[1658]: Negative trust anchors: home.arpa 10.in-addr.arpa 16.172.in-ad>
Apr 20 23:49:17 x570-fedora-amac systemd-resolved[1658]: Using system hostname ‘x570-fedora-amac’.
Apr 20 23:49:17 x570-fedora-amac systemd[1]: Started systemd-resolved.service - Network Name Resolution.
Apr 20 23:49:21 x570-fedora-amac systemd-resolved[1658]: enp38s0: Bus client set default route setting: yes
Apr 20 23:49:21 x570-fedora-amac systemd-resolved[1658]: enp38s0: Bus client set DNS server list to: 8.8.8.8
Apr 20 23:49:22 x570-fedora-amac systemd-resolved[1658]: enp38s0: Bus client set DNS server list to: 8.8.8.8, fe80::1
Apr 20 23:49:28 x570-fedora-amac systemd-resolved[1658]: Clock change detected. Flushing caches.
Apr 20 23:52:05 x570-fedora-amac systemd-resolved[1658]: enp38s0: Bus client set DNS server list to: fe80::1
Apr 20 23:52:07 x570-fedora-amac systemd-resolved[1658]: Using degraded feature set UDP instead of UDP+EDNS0 for DNS se>
lines 1-27/27 (END)
$ journalctl --no-pager -b -u systemd-resolved.service
Apr 20 23:49:17 x570-fedora-amac systemd[1]: Starting systemd-resolved.service - Network Name Resolution…
Apr 20 23:49:17 x570-fedora-amac systemd-resolved[1658]: Positive Trust Anchors:
Apr 20 23:49:17 x570-fedora-amac systemd-resolved[1658]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc683457104237c7f8ec8d
Apr 20 23:49:17 x570-fedora-amac systemd-resolved[1658]: Negative trust anchors: home.arpa 10.in-addr.arpa 16.172.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa 168.192.in-addr.arpa d.f.ip6.arpa corp home internal intranet lan local private test
Apr 20 23:49:17 x570-fedora-amac systemd-resolved[1658]: Using system hostname ‘x570-fedora-amac’.
Apr 20 23:49:17 x570-fedora-amac systemd[1]: Started systemd-resolved.service - Network Name Resolution.
Apr 20 23:49:21 x570-fedora-amac systemd-resolved[1658]: enp38s0: Bus client set default route setting: yes
Apr 20 23:49:21 x570-fedora-amac systemd-resolved[1658]: enp38s0: Bus client set DNS server list to: 8.8.8.8
Apr 20 23:49:22 x570-fedora-amac systemd-resolved[1658]: enp38s0: Bus client set DNS server list to: 8.8.8.8, fe80::1
Apr 20 23:49:28 x570-fedora-amac systemd-resolved[1658]: Clock change detected. Flushing caches.
Apr 20 23:52:05 x570-fedora-amac systemd-resolved[1658]: enp38s0: Bus client set DNS server list to: fe80::1
Apr 20 23:52:07 x570-fedora-amac systemd-resolved[1658]: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server fe80::1%2.
Disabling IPv6 and putting 192.168.100.1 DNS4 works now. If DN4 is on automatic, it’s not working.
As for disabling IPv6 on GPON ONT / router, it is locked by my ISP so I don’t have that option to do so. I do run switches to connect all my PC/NAS/CCTV/Mesh WiFi stuff.