Is it possible to replace the DHCP and DNS functionality of your ISP router with a raspberry-pi/pi hole? (More specifically, does DHCP include DNS?)

Question

I have a raspberry pi currently set up with Pi-Hole. Unfortunately, I cannot change the DNS settings on my ISP provided router (called a "Funbox 3.0"). It has a DNS tab with textboxes for "primary IPv4 DNS" and "secondary IPv4 DNS", but they're greyed out and cannot be modified.

This means I can't automagically have all devices on my network use the Pi-Hole for DNS instead of the router.

Are these DNS settings part of the DHCP protocol, or are they a separate thing? i.e. If I turn off DHCP on my router and then turn it on in Pi-Hole, will the DNS settings now also also point to the Pi-Hole?

Disabling DHCP won’t achieve your goal – Ramhound Feb 23 '22 at 12:43 — Ramhound, Feb 23 '22 at 12:43
Use your own router rather than the isp supplied one. – Bib Feb 23 '22 at 13:58 — Bib, Feb 23 '22 at 13:58

score 1 · Accepted Answer · answered Feb 23 '22 at 13:58

Typically, a DHCP server supplies devices with the at least following:

an IP address
the subnet mask
the IP address of the router responsible for communication outside the subnet
the time this is valid for
and important for this: the address of at least one DNS server(which the client does not have to use)

PiHole does include its own optional DHCP server. I did run this exact setup successfully for a few years.

There is also a Tutorial on the pi-hole forum with detailed instructions, and they explicitly state this as a potential solution to your problem.

score 0 · Answer 2 · answered Feb 23 '22 at 13:31

0

Even if you cannot change the DNS setting on the router, nothing prevents you for setting a different DNS server on each of your devices.

You can therefore set your computers to use your own internal DNS server. This won't conflict with the router of the ISP.

answered Feb 23 '22 at 13:31

harrymc

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I know, but the key word here is "automagically" I want it to *just work*. – Dan Forever Feb 23 '22 at 14:54
The DNS and DHCP are coupled in a router. You might be able to turn DHCP off, but it might be that both are impossible. – harrymc Feb 23 '22 at 19:06

score 0 · Answer 3 · answered Feb 23 '22 at 14:00

DHCP and DNS are 2 separate services.
However: In most cases the DHCP server tells the DHCP clients which DNS servers to use.

If you can't configure the provider router to supply your own DNS server to the clients there are basically 2 solutions:

You can always configure your clients to use an alternative DNS server (your pihole) if you are willing to manually configure each client (and this can be a major hassle in some cases).
The most flexible option is to setup your own DHCP server that supplies ip-adresses and the DNS settings to the clients, but this is only feasible if the DHCP in the provider-router can be completely turned OFF. If it remains running you will have 2 DHCP servers on your network, which will cause major problems.
(The DHCP can be done on the pi in parallel to its pihole functionality.)

Is it possible to replace the DHCP and DNS functionality of your ISP router with a raspberry-pi/pi hole? (More specifically, does DHCP include DNS?)

3 Answers3