Setting an explicit DNS server with DHCP breaks name resolution

miicah · Jul 3rd 2025

Recently got my OMV server up and running after some hardware issues only to find it couldn't connect to apt-get or resolve any hostnames (except local ones).

After a bunch of troubleshooting I realised that if I have a DNS server set in 'Advanced settings' and use DHCP, the resolver breaks completely. Removing the DNS server fixes this issue.

This is a bug right?

I'm running a clean install (from the ISO) of 7.7.4-1 (Sandworm).

votdev · Jul 3rd 2025

Quote from miicah

This is a bug right?

That should actually work. But I can't say what netplan and then systemd-networkd/systemd-resolved do with it.

ryecoaaron · Jul 3rd 2025

I am able to set a dns server on a system using dhcp with no issues. What is the output of with the dns server set and not set: ip route show

votdev · Jul 3rd 2025

What is the output of

Bash

# resolvectl status
# journalctl -u systemd-resolved

miicah · Jul 5th 2025

Quote from ryecoaaron

I am able to set a dns server on a system using dhcp with no issues. What is the output of with the dns server set and not set: ip route show

With no DNS server set:

default via 10.0.0.254 dev eno1 proto dhcp src 10.0.0.1 metric 100

10.0.0.0/24 dev eno1 proto kernel scope link src 10.0.0.1 metric 100

10.0.0.249 dev eno1 proto dhcp scope link src 10.0.0.1 metric 100

10.0.0.254 dev eno1 proto dhcp scope link src 10.0.0.1 metric 100

But now that I try to set the value through the GUI it won't let me; when I click apply config changes it just sits at please wait indefintely.

The only change from yesterday is I managed to get the latest kernel working (6.12), I was on 6.1.33 before.

miicah · Jul 5th 2025

Actually it's broken again, DNS server not set in GUI.

Code

Jul 05 21:05:48 omv systemd-resolved[650]: Using degraded feature set UDP instead of UDP+EDNS0 for DNS server 10.0.0.24>
Jul 05 21:05:48 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:05:48 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:05:53 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:05:53 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:05:53 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:05:53 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:05:56 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:05:56 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:05:58 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:05:58 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:05:58 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:05:58 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:05:59 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:05:59 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:05:59 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:05:59 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:00 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:00 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:01 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:01 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:01 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:01 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:04 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:04 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:05 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:05 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:05 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:05 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:06 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:06 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:06 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:06 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:10 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:10 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:10 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:10 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
Jul 05 21:06:32 omv systemd-resolved[650]: Using degraded feature set TCP instead of UDP for DNS server 10.0.0.249.
Jul 05 21:06:32 omv systemd-resolved[650]: Using degraded feature set UDP instead of TCP for DNS server 10.0.0.249.
root@omv:~# ip route show
default via 10.0.0.254 dev eno1 proto dhcp src 10.0.0.1 metric 100
10.0.0.0/24 dev eno1 proto kernel scope link src 10.0.0.1 metric 100
10.0.0.249 dev eno1 proto dhcp scope link src 10.0.0.1 metric 100
10.0.0.254 dev eno1 proto dhcp scope link src 10.0.0.1 metric 100
root@omv:~# ping google.com
ping: google.com: Name or service not known

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Setting an explicit DNS server with DHCP breaks name resolution

votdev Jul 3rd 2025

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