DNS service starting before network service is online?

[hwwilliams]

Technitium DNS service has the following

After=network.target
Wants=network-online.target

Wants is a soft requirement, if it fails DNS still starts but even if it's just not done yet DNS doesn't wait for it either which can result in failure to bind addresses that may not be assigned to interfaces yet.

I had an issue recently where my 3 DNS servers lost power and when they came up all appeared to be fine locally as I could reach the internet and use DNS but when remote services tried to reach the DNS server it got connection refused messages.

I had configured the following setting

I've since changed this to 0.0.0.0:53 and [::]:53 because I don't actually need it to be bound to .2 specifically but when it was bound and the network didn't come up quickly enough Technitium failed to bind because the address wasn't available yet

[2026-08-10 23:25:13 UTC] DNS Server is loading block list zone...
[2026-08-10 23:25:13 UTC] DNS Server is reading block list from: https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts
[2026-08-10 23:25:14 UTC] [192.168.1.2:53] [UDP] DNS Server failed to bind.
Cannot assign requested address
[2026-08-10 23:25:14 UTC] [192.168.1.2:538] [UDPPROXY] DNS Server failed to bind.
Cannot assign requested address
[2026-08-10 23:25:14 UTC] [192.168.1.2:53] [TCP] DNS Server failed to bind.
Cannot assign requested address
[2026-08-10 23:25:14 UTC] [192.168.1.2:538] [TCPPROXY] DNS Server failed to bind.
Cannot assign requested address
[2026-08-10 23:25:14 UTC] [[::]:53] [UDP] DNS Server was bound successfully.
[2026-08-10 23:25:14 UTC] [[::]:538] [UDPPROXY] DNS Server was bound successfully.
[2026-08-10 23:25:14 UTC] [[::]:53] [TCP] DNS Server was bound successfully.
[2026-08-10 23:25:14 UTC] [[::]:538] [TCPPROXY] DNS Server was bound successfully.

A reboot of the server did fix the issue at the time.

I think the corrected service settings would be

Wants=network-online.target
After=network-online.target

I can't see a situation where DNS would be useful before the network is online but let me know if this is something I'll have to add into my own installation process to avoid in the future.

[arthur-2sheds-jackson]

Set
net.ipv4.ip_nonlocal_bind = 1
and/or
net.ipv6.ip_nonlocal_bind = 1
in sysctl.

[ShreyasZare]

Thanks for the post. It is recommended to use the 0.0.0.0 and [::] as local end points to avoid such issues.

The change you suggest may not work for all scenarios where the DNS server itself does not have routable network and is just used for local authoritative DNS. In such case, the service wont come up even when network interface has an IP address.

[vichmartins]

@ShreyasZare I've had this issue happen to me as well. In my case I need to have the specific IP set for a specific interface due to certain network requirements and company policies. My solution was to set this manually in the service file.

Would you consider making this a optinal GUI setting toggle. The default behaviour would be what it currently is, but the toggle would set what @hwwilliams suggested within the Settings tab?

[ShreyasZare]

@vichmartins Thanks for the suggestion. However, it is not possible to have a GUI option since the DNS server can be installed in many different platforms and such a option is very specific to one kind of installation.