fresh install of pi-hole on fresh Raspi breaking after router DNS pointed to it

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1

My previous instance of PiHole v5.x (updated recently, so whatever was likely the newest version previously), went from blocking 30% of requests to 3%, so I thought perhaps there was something wrong.

Took the opportunity to re-image my Raspbery PI 4, installing the latest headless Rasperry PI x64 OS. Run apt update & apt full-upgrade first, then install pi-hole per the "One-Step Automated Install" suggestion on the site. At this point, everything seems to be working as expected.

My Router has DHCP enabled and my raspi is set to a static (or "reserved", as my router calls it) IP. Next I change my Router's primary and secondary DNS servers to point to that same IP.

As soon as I do that, the raspi loses all connectivity. I can't ping any outside URLs or IPs, nor even internal IPs; although I can still SSH into the raspi. This includes after setting the router back to its default DNS settings.

I'm moderately proficient with Linux, but even with ChatGPT's help, there's nothing I seem to be able to do to restore connectivity on the raspi without re-imaging it; which I have now done 3 times in a row with the same result; so I figured I'd try here. I thought perhaps pointing my router's DNS to the raspi was resulting in a loop where the raspi was pointing back to the router, which pointed back to itself; but everything chatGPT has suggested I look at does not seem to show that being the case. But I'm not sure where else to look at this point.

It's worth noting that in my previously working configuration on v5 had my raspi serving as the DHCP server as well, but for some reason that also isn't working.

I am currently in the process of re-imaging the raspi again, so I can't post the "pihole -d" log, but I'm not sure trying the same thing over again is going to help. Happy to do it if someone thinks it'll help but perhaps someone has heard of this before?

2

What's your router's make and model?

3

It's called "Home Hub 3000" and is the default modem/router provided by my ISP:

With a bit of research it appears to be a rebranded "Sagemcom Fast 5566".

I have a TP-Link AX6000 (Archer AX80) hardwired to it and acting as an access point, but that's not what I'd be configuring pihole through.

4

How did you configure your router to make use of Pi-hole?

Some routers disagree with having their upstream DNS servers set to private range IPs, and some would even shift their internal network when detecting such a change.

Often, having those routers distribute Pi-hole as local DNS server via DHCP avoids that issue.

5

This is a rather old / long thread about the Home Hub 3000. It might provide additional insight.

6

@Bucking_Horn,

since originally posting my question, I re-imaged the raspi and was still getting the connectivity issue, so that led me back to the router. After a factory reset of that, it's back up and running again, so it's likely a router issue, and despite reverting my changes in the router itself via the GUI, there appears to be something in the settings that persists regardless; as only a factory reset seems to solve it. Nonetheless, to answer your question:

After fresh install of Rasperry Pi OS Lite x64, and after apt update / apt full-upgrade / install pihole with default settings:

  1. log into router GUI
  2. click into the section on connected devices, and locate the raspi by IP / MAC. Select it, and change the "IP Type" associated with it from "Dynamic" to "Reserved". I can specify the IP at this point, but so far I've been leaving it as whatever DHCP set it to initially. Save those changes
  3. Go to DNS settings, which defaults to "Obtain DNS information automatically.". I select "Manually specify DNS information." and enter the IP associated with the Raspi (and which has been "reserved" in step 2 above) for both the primary and secondary DNS servers. There's a 3rd field called "Host name" containing "mynetwork,monreseau,home" which I've just been leaving unchanged. I suspect that is just the hostname for the router itself. Save those changes

at this point, the raspi loses all connectivity to anything. Anything else on the network also loses connectivity (likely because the raspi itself has). If I revert the DNS settings back to the default (automatic), other devices on the network go back to working properly, but the raspi does not. I tried setting the IP back to dynamic, and that doesn't fix it. rebooting it, or the router doesn't fix it. Only, apparently, after factory resetting the router does it work again.

@CallMeCurious might be on to something here.. As noted in my original post when I was running the older version of pihole I had it set up as the DHCP server; although without the second step he indicated. I did actually try that again with the latest version but it also failed; but I think this time around I'll try exactly what that post described and report back

EDIT: no dice. I set the DHCP settings exactly the same as what had been on the router (router @ 192.168.2.1, IP range 192.168.2.10 - 192.168.2.254) and added the static DHCP setting per that thread, eg:
MAC,StaticIP,hostname

then enabled DHCP on the raspi and disabled DHCP on the router (after having made sure the lease time was only a few mins and clearing all existing leases prior). Once everything reconnected I was getting IPs that were outside of the range set.. Like my iphone picked up 192.168.0.71 with no internet connectivity. The raspi had no "inet" IP under eth0 when I ran ifconfig.

reverting the router back to providing DHCP and disabling on pihole at least got it fixed. and connectivity on the raspi is at least still working now

7

This is for the HH 4000 but this reddit solution might work. Essentially its running two dhcp servers. HH 3000 would have a range of 1 ( pihole ) and Pihole runs DHCP for all else. Link is here to that post..

8

This appears to have worked! I'll keep monitoring through the evening, but so far so good.

I am seeing this show up under Pi-hole diagnosis:
Warning in dnsmasq core:
not using configured address 192.168.2.10 because it is in use by the server or relay

idk if this helps - I ran pihole -d and it gave me this:
https://tricorder.pi-hole.net/oPMKU4n7/

but I'm not sure how to access it, I just get a blank page.

9

Read this:

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When you can access the debug locally at

/var/log/pihole/pihole_debug.log

11

This link is available only to Pi-hole team.

As explained by CallMeCurious, you will find you own local log in /var/log/pihole/pihole_debug.log

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