My NetworkManager connects to the internet but I do not have any internet access due to a bad DNS configuration. I do not have much experience with DNS settings, but it appears the issue is with systemd-resolved. I can ping IP addresses directly (e.g. 8.8.8.8) and get a response normally, but I cannot resolve domains when using the default configuration below. I have tried a symlink to the three configuration modes listed in the systemd-resolved docs, but none of them work.

Cannot resolve any domain with the following, but I can ping IPs (tried a bunch and they all work) without any issues.

# /etc/resolv.conf 

nameserver 127.0.0.53

options edns0 trust-ad

I also get timeout errors when using dig or host.

; <<>> DiG 9.16.1-Ubuntu <<>> www.ubuntu.com

;; global options: +cmd

;; connection timed out; no servers could be reached

I can get domain resolution and connect to the internet by changing the resolv.conf nameserver to 8.8.8.8, but resolution takes a long time, with a web page taking >1 min to load even with network speed tests reporting over 100 mbps and ping <30 ms on the same machine.

The configuration below works, sort of, with really slow response times

# /etc/resolv.conf 

nameserver 8.8.8.8

options edns0 trust-ad

Additional info that might be helpful

Like I said, I am new to these systems and I am struggling to troubleshoot the issue. Below is everything that I think might be useful. All outputs below are using nameserver 127.0.0.53

Ubuntu 20.04.3 LTS

Output of systemd-resolve --status

Global

       LLMNR setting: no                  

MulticastDNS setting: no                  

  DNSOverTLS setting: no                  

      DNSSEC setting: no                  

    DNSSEC supported: no                  

          DNSSEC NTA: 10.in-addr.arpa     

                      16.172.in-addr.arpa 

                      168.192.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 

                      corp                

                      d.f.ip6.arpa        

                      home                

                      internal            

                      intranet            

                      lan                 

                      local               

                      private             

                      test                



Link 3 (ipv6leakintrf0)

      Current Scopes: DNS

DefaultRoute setting: yes

       LLMNR setting: yes

MulticastDNS setting: no 

  DNSOverTLS setting: no 

      DNSSEC setting: no 

    DNSSEC supported: no 

  Current DNS Server: ::1

         DNS Servers: ::1

          DNS Domain: ~. 



Link 2 (wlo1)

      Current Scopes: none

DefaultRoute setting: no  

       LLMNR setting: yes 

MulticastDNS setting: no  

  DNSOverTLS setting: no  

      DNSSEC setting: no  

    DNSSEC supported: no  

# /etc/systemd/resolved.conf 

[Resolve]

#DNS=

#FallbackDNS=

#Domains=

#LLMNR=no

#MulticastDNS=no

#DNSSEC=no

#DNSOverTLS=no

#Cache=no-negative

#DNSStubListener=yes

#ReadEtcHosts=yes

# NetworkManager configuration: /etc/NetworkManager/NetworkManager.conf (lib: 10-dns-resolved.conf, 20-connectivity-ubuntu.conf, no-mac-addr-change.conf) (run: 10-globally-managed-devices.conf) (etc: default-wifi-powersave-on.conf)



[main]

# rc-manager=symlink

# auth-polkit=true

# dhcp=internal

dns=systemd-resolved

plugins=ifupdown,keyfile



[connectivity]

uri=http://connectivity-check.ubuntu.com/



[ifupdown]

managed=false



[logging]

# backend=journal

# audit=true



[device]

wifi.scan-rand-mac-address=no



[device-mac-addr-change-wifi]

match-device=driver:rtl8723bs,driver:rtl8189es,driver:r8188eu,driver:8188eu,driver:eagle_sdio,driver:wl

wifi.scan-rand-mac-address=no



[connection]

wifi.powersave=3



# no-auto-default file "/var/lib/NetworkManager/no-auto-default.state"

The system log on startup

 Starting Network Name Resolution...

sisyphus systemd-resolved[6024]: Positive Trust Anchors:

sisyphus systemd-resolved[6024]: . IN DS 20326 8 2 e17f45b80b8f1d39a95f0b0d7c45a08458e880409bbc683457104237c7f8ec8d

sisyphus systemd-resolved[6024]: Negative trust anchors: 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

sisyphus systemd-resolved[6024]: Using system hostname 'sisyphus'.

The system log in debug mode outputs the following, switching between UDP and TCP protocols.

Transaction 33247 for <ntp.ubuntu.com IN A> scope dns on ipv6leakintrf0/*.

systemd-resolved[4805]: Using feature level TCP for transaction 33247.

systemd-resolved[4805]: Sending query via TCP since UDP isn't supported.

systemd-resolved[4805]: Using feature level TCP for transaction 33247.

systemd-resolved[4805]: Connection failure for DNS TCP stream: Connection refused

systemd-resolved[4805]: Retrying transaction 33247.