Newbie to Linux here. Been using FreeBSD for almost 10 years, so not new to CLI or anything, just new to Debian/Raspbian/Linux. Thankfully its relatively easy to move from BSD to linux and figure things out, minus stuff for systemd, which is still quite different from FreeBSD.
I have an opnsense machine that I previously used for my home network. It handled all DNS and DHCP requests. This is all still true, except I have chosen to have all of my machines that connect via DHCP go to my raspberry pi for filtering with pihole. I set it up about 4 or 5 months ago and it worked fine, until I had to reboot the raspberry pi.
I’ve now noticed that when I reboot the Pi, it seems to selectively decide to not listen to some DNS requests, for anywhere from a few minutes to a few hours, depending. I have been unable to determine the cause, nor how to fix it, nor have I figured out how to make it fix itself, except to simply stop using the DNS on my pi until it starts working. Tonight, I did some package updates followed by a reboot, and then spent 2 hours trying to figure out what was wrong with Minecraft, only to figure out it was a DNS issue. G/F hates me right now since Minecraft wouldn’t run (first thing the launcher does is go to the internet to validate files, which the DNS failed and so it would crash out).
I’ve used tcpdump and wireshark to validate that my dns requests are leaving my desktop and also verified they are received by the pi, but there is no response packet being sent back. (See screenshot)
There is a possibility that I’ve screwed up the Pi’s networking, and this is some artifact of that. When I first setup this pi, I tried to give it a static IP and static DNS entries. However, since I have to use Raspbian Buster, and I couldn’t figure out how to get it to work properly, I instead opted to give it a static IP via DHCP. So this could be a remnant of that.
I expect that on reboot, that pihole should come up within a minute or two and start working, serving DNS requests.
pihole seems to be up (accessible via WebGUI, no indication of problems I can see), and all seems to be completely fine and normal, but DNS requests are ignored. After some indeterminate period of time pihole will randomly start working. I’ve had it start working after 5 minutes, sometimes after a few hours. There’s nothing I’ve been able to figure out as to how to make it do whatever it does to start working, it just randomly starts working.
Thanks to whoever took the time to read this far.