this post was submitted on 11 Jul 2023
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What to use as DHCP server? (self.selfhosted)
submitted 1 year ago by k86k to c/selfhosted
29 comments fedilink hide all child comments
 

Hello everyone,

first time ever posting on lemmy, feels good 😉

I have a question regarding DHCP in my local network.

My current setup is as follows:

  • DHCP provided by router (Fritz!Box 7490)
  • DNS provided by pi-hole hosted on a raspberry pi
  • DHCP pushes the IP of the raspberry via DHCP to all clients

My problem is: When the raspberry pi (running pi hole) is down for any reason, none of my devices has internet access anymore. This is due to the fact that the Fritz!Box router (aka DHCP server) has no option to push a secondary DNS as a fallback to its clients.

One option would be to buy another router which has the option to push a secondary DNS, which I would prefer to avoid, since otherwise I am happy with the Fritz!Box.

So I am looking for alternative configurations with my existing hardware. I could for example use pi holes DHCP. Or I could use the DHCP server package of a synology NAS which is also part of my local network. Or is there another option, maybe using some DHCP service on the raspberry pi or in a docker container or something like that? Does anyone have experience with one of these setups and can tell me if it is possible to provide the clients with two (prioritized) DNS options? What would you recommend? Thanks!

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[–] h0rnman 4 points 1 year ago (2 children)

OP already said that their current DHCP solution (the router) can't push multiple DNS servers. Having a good secondary can be really helpful for things like power blips, maintenance windows, and cats pulling power cables. There are a few solutions that also do ad blocking that can make good secondaries

[–] PineapplePartisan 7 points 1 year ago (1 children)

I don’t think anyone is arguing against dual DNS servers. The distinction being made is that a second DNS server is not a fallback. Most newbies think “secondary” means it will only be used when the primary is unavailable. That’s not true. A client is just as likely to use a secondary DNS as a primary. If only one DNS uses pihole, then the secondary will serve ads because it’s just calling the upstream DNS resolver.

Personally, I accomplished what OP is talking about with two rPis. First serves DCHP from 192.168.1.10 to .100, second serves .101 to .250. I send the two piholes as primary and secondary DNS. I also use Unbound as the upstream, but that is just personal preference.

[–] h0rnman 2 points 1 year ago

Depending on the client, it can be. The Microsoft page pretty cleanly defines expected dns client behavior [https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/dns-client-resolution-timeouts#what-is-the-default-behavior-of-a-windows-7-or-windows-8-dns-client-when-two-dns-servers-are-configured-on-the-nic](Microsoft learn). There haven't been any published changes to this that I've seen, and it more or less matches my experience. Linux is a lawless land in this respect, but it really boils down to "it might", so caveat emptor there. That's also why I suggested a public ad blocking dns server as a secondary, in case multicast dns does its multicast dns thing