Ubunut 22.04: DNS fails to resolve certain names

Marco

7/10/24, 7:42 AM

Navigating to some sites with Firefox I noticed that sometimes the images are not displayed. Initially I tought it was a site issue or something related to the AdBlocker, then I used Firefox on Windows 11 and the same sites are displaying everything correctly. In one case, Ubuntu failed to navigate to a certain site at all while working without problems with Windows 11.

After investigating a bit, the cause doesn't seems related to Firefox, using nslookup or dig shows that the DNS fails to resolve the domain names.

Both machines, Ubuntu and Windows 11, are using the same connection (4G mobile) and the same DNS settings (OpenDNS). I can use them in side-by-side and while Windows 11 works, Ubuntu fails to resolve some sites or part of them.

As far as I can tell, the configuration is correct, otherwise it won't be able to resolve anything. Seems that somehow, certain domains fails when the request comes from a Linux machine (would that even be possible ?). So far only two sites are failing, all "most used sites" like Google, Youtube, etc. are working without problems, so not really a blocker, just a weird issue.

What can I do to try to better understand what happens ? And more important how to fix ?

Thanks for any help.

1 + 2

networking

dns

ckhan

7/10/24, 9:44 AM

You're sure using the same DNS server for both machines? Try using a public resolver, like 1.1.1.1 with `dig @1.1.1.1 bustedhost.com` and see what comes back?

Marco

7/10/24, 4:50 PM

Of course I'm sure. However, I tried to use dig @opendnsip and that works. Seems that it fails when routed through whatever handles the default local nameserver at 127.0.0.53. The funny thing is that both are actually resolving, only 127.0.0.53 returns SERVFAIL (but the data are there).

Score:0

Ubuntu

Pihhan

7/11/24, 1:17 PM

Consider trying DNS=dnsmasq in Network manager.conf. Instead of using systemd-resolved, try less broken local server instead. You would have to remove /etc/resolv.conf symlink, then restarting NetworkManager.service.

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