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?
Run two and check the logs. You’ll see about 20% of your requests will log on the second instance. So currently, that’s 20% of your DNS requests not being filtered.
You’ll also find some devices just latch on the the second and never use the first - again, in your scenario, these are not being filtered.
I can back this up with experience.
I’m actively running two piholes for years now. About 2/3rds of my traffic does go to the primary and some seem to ‘lock on’ to using just one, but most devices will swap between the two at their leisure.