It’s called split DNS. Can be implemented using dnsmasq

It can be implemented with dnsmasq but dnsmasq doesn't integrate with DHCP (edit, client) out of the box and requires a restart to apply configuration updates which invalidates query cache.

Edit-

I think split dns more commonly refers to serving different internal/private and external/public zones.

In this case, the DNS servers may return the same results but if I'm connecting to a VPN running some distance away, I don't want to route all DNS requests to that server--only the ones for domains on that network. The Domains directive allows configuring this https://man.archlinux.org/man/systemd.network.5#%5BNETWORK%5...

You can add a dhclient hook to reconfigure dnsmasq with `server=` directives to achieve the same thing, but, as mentioned, that still requires restarting the dnsmasq daemon. That usually manifests as: the VPN connection times out, the hook runs, dnsmasq is restarted, but a random web page or request will fail while the daemon is restarting. Sure, you could do SO_REUSEADDR or something to prevent the disruption, but, once again, this all just works out of the box with systemd-*

> dnsmasq doesn't integrate with DHCP

DNSMasq is a combined DNS and DHCP server! Of course it's integrated!

I'm talking about a local caching resolver, not a server running somewhere else on the network. dnsmasq doesn't ship with a DHCP client

I don't get your point. DNSMasq doesn't ship with a client, because it's a server. It's a cacheing resolver and a DHCP server that is usually run locally. I don't know of any system that doesn't come with its own built-in (or standard) DHCP client.

Can you clarify your objection to DNSMasq?

His objection is that it doesn't replace the use case that resolvd is supposed to solve. Which is to provide a local service that can redirect DNS queries dynamically as local interfaces go up and down, which is where the integration with a DHCP client comes in.

Oh, OK. Thanks.

Makes sense; a lot of the systemd ecosphere seems to be about hotdesking, plugging things in and unplugging them, moving from one wifi AP to another, hibernating and so on. I don't encounter these use-cases, on the whole, which is probably a large part of why I find systemd so annoying.

Yeah, and I have some sympathies with what systemd is trying to do here, but the implementation is often backwards and/or half-arsed.

Still no DHCPRELEASE.

Dnsmasq and resolvd is a beast to tame in homelab, and split network.

> I'm not overly found of timer units, either. They seem feature rich but much more complicated to setup than a single line in a crontab.

I’ve twice tried to use them. Closest I got to having one work was that it reported it ran, and didn’t error, but it did not run. Extremely simple cases that were basically copy-paste an example and barely modify it, too.

Oh well, add a line in cron and forget about it.