I have configured Pi Hole on a Pi Zero W and its local address is 192.168.1.254. My router acts as the DHCP server although the Pi Hole has a reserved IP address. I have manually configured certain of my network devices to use 192.168.1.254 as their DNS (rather than configuring the DNS of the router to use 192.168.1.254 and rely on the DHCP to announce this DNS address to all devices on my network).
The internet on my local computers where the DNS is 192.168.1.254 seem to work initially, then, after a short period of time, they can no longer access the internet. This seems to occur on all devices which I have manually configured the DNS to be 192.168.1.254. If I use my ISP DNS address announced by the DHCP - i.e. bypass my Pi Hole - I do not have an issue at all with accessing the internet.
From a PC on my network I have tried pinging 192.168.1.254 and I get a continuous reply for a while - then a continuous request timed out for while - effectively coinciding with when the internet works. So something is intermittently stopping the Pi Hole communicating with the devices on my network.
From my Pi Hole I have pinged:
google.com and it seems to get a consistent successful reply
devices on my network and I seem to get some replies where the network is unreachable, others where the destination host is unreachable.
I have run a Pi Hole repair, rebooted etc and it hasn't made any difference.
From your description, I understand that devices intermittently lose connectivity to your Pi-hole, which happens to run on an RPi Zero W, after a more or less prolongued period of sustained flawless operation.
If you have connected your Pi-hole over WiFi., there are a number of issues that could interfere.
Without claiming to be exhaustive:
The Zero W is using the 2.4GHz band exclusively, which might be quite congested (e.g. if you were living in an apartment building), and your router may switch channels to escape congestion, forcing your devices to follow.
Normally, that should only take a very limited time, barely noticeable. But your Zero's WiFi might switch to channels that are not available for usage in your country if you didn't setup your WiFi country correctly.
You should also check your router for options related to possible channel usage restrictions.
Other smart device protocols like ZigBee or Bluetooth operate at frequencies that may overlap with some channels in the 2.4GHz band as well, causing interference.
In rare cases, the same might be true if you operate electrical 'noisy' or 'dirty' devices (e.g. micowave ovens) close to your router or your RPi.
And finally, public weather or military radar devices operating in your vicinity might force all other communication on certain reserved channels to cease completely for a few minutes. Some router models may list these privileged usages in their logs.
In all cases, it might be tricky to confirm the actual cause of your outages.
Even if you would be able to isolate a completely different cause for your outages:
If your budget allows, I would recommend procuring a quality Ethernet dongle, which will enhance connection quality as well as latency at the same time (stay away from cheap Chinese models sporting 9700 in their name, fotos or description).
Thanks v much - I tried that - things seem to be working better on the ethernet dongle, but I'll monitor it to see if there are any outages.
one strange thing - I have been running an indefinite ping to the ethernet address of the raspberyy pi from another device on the network - I consistently get ping times of 1-3ms, except every once in a while i get 3 or so consecutive pings where the time is 200-300ms, then it goes back to normal. Why would this be?