I have an asus router with a pi-hole on the network.
I was doing some work on my server and noticed that when pi-hole was down, I couldn’t access the internet. I was looking for some ideas online how to deal with this, but they said to have a second pihole on the network in case one is offline. Is that the only way to do it? Is there any way to have the network go back to normal if the pihole is offline?
I don’t think this accomplishes what he wants. The router DHCP will assign the second DNS address as you mention, but the devices will select one at random, not as a backup/failover. So what happens is that devices sometimes go through the Pi-hole and sometimes go through the secondary DNS address and receive ads. The only real way I’m aware of is to have a second pi-hole for redundancy. Personally, I decided to use a cloud based service (NextDNS) for this exact reason. I didn’t want my families internet to rely on devices that I host.
I think it depends. In my limited experience, because I have not tested this thoroughly, most systems pick the first DNS adresses and only send requests to the second if first doesn’t respond.
This has lead at least a couple of times to extremely long timeouts making me think the system is unresponsive, especially with things like kerberos ssh login and such.
I personally set up my DHCP to provide pihole as primary, and my off site IPA master as secondary (so I still have internal split brain DNS working in case the entire VM host goes down).
Now I kinda want to test if that offsite DNS gets any requests in normal use. Maybe would explain some ad leaks on twitch.tv (likely twitch just using the same hosts for video and ads, but who knows).
Edit: If that is indeed the case, I’m not looking forward to maintaining another pihole offsite. Ehhh.
It is entirely the case.
DNS queries will go to all on the list, and use whatever responds first.
If you are seeing occasional ad leaks, this is why.
When it comes to a “secondary”DNS… there is nothing like a primary and secondary DNS server. These indications are quite misleading but many systems adopted it this way. Pihole only list the DNS servers as primary and secondary, because this is what the providers write on their pages. The bad phrasing is supported especially by how Windows handles it.
Most operating systems implement DNS servers as alternatives, not as fallbacks, i.e. they will query any of both servers from time to time, so it is quite likely that you will loose your Pi-hole filtering capabilities (at least partially) [if you specify a secondary DNS server on your network].
The ONLY DNS server you should have set on your network is a/the PiHole(s).
How many queries a month do you have? I’m at 15 days and I’m already at 750K. Do you pay for your service? I can do that, just curious what is common.
I’m at 30k blocked per day, over 100k queries per day.
This on a small 2 user network, with a handful of machines, but a fucking Samsung TV. That goddamn thing constantly pings all sorts of shit.
If I really restrict it (breaking some stuff on the TV), I can get to 35% of queries blocked per day, mostly from it.
Though nominal blocking kills the ads on the menu system, pretty well, making it much more responsive.
I’m not exactly sure how many queries, but it’s above the free limit. I purchased the pro plan. For $20 a year and it’s been a great service for me. I can send a referral code for 30% off (I think). I think adguard has a similar service.