Pi.hole/admin returns ERR_NAME_NOT_RESOLVED but querries are still being logged

[RamSet]

@lzy7071

that my router sometimes switch to the secondary DNS

That is a common issue with routers demanding a secondary DNS to be set up. It sometimes bleeds requests through that DNS and adblocking basically doesn't work.

Primary vs. Secondary DNS

Following the regulations, there is nothing like a primary and secondary DNS server. These indications are quite misleading but many systems adopted it this way. We 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. If you look at any Linux distribution, there is usually no separation between primary and secondary, but you can only provide a comma-separated list of DNS se…

You could set-up a raspberry pi zero w as your backup DNS (with Pi-hole running) and that way you'll have a Pi-holed backup DNS (when and if, the first one fails).

Or see if the router takes a bogus IP under your secondary. The only downside of this is that if Pi-hole is offline, you don't have DNS resolution.

Here is some relevant info:

Why should Pi-hole be my only DNS server?

Reduced Ad Blocking Capability The main reason you should Pi-hole as your only DNS server is that you will see increased performance in the blocking of ads. If you have two DNS servers (Pi-hole and something else), your network clients may not always query Pi-hole for name resolution. If a query happens to be answered from a non-Pi-hole DNS server, your block lists will not apply (since that DNS server doesn't know about them). All Queries Need To Go Through Pi-hole First Since other DNS serv…