Cloudflare's DNS causes my router to think it's offline

When I switch to Cloudflare’s DNS in my router, it keeps showing that it’s offline even though internet traffic works fine, I can access websites, video streaming etc, even online gaming works fine.

My physical location: Shillong, Meghalaya, India
My ISP: BSNL FTTH
My ONT: TP-LINK XN020-G3v (set up in bridge mode)
My Router: TP-LINK Archer D2 (handles PPPoE)

With Cloudflare:

With a different DNS provider:

Traceroute:

Ping Test:

Time bump…

Can anyone help me out with this?

Your router probably tries to resolve a given address to decide whether it’s connected or not. For whatever reason it can’t resolve the address using 1.1.1.1 but it can with 8.8.8.8.

Would be interesting to know which address it is trying to resolve. You could either set-up your own DNS server (for testing, a raspberry pi will do) and use that as your router’s DNS. If you log the received queries, you will know what the router is trying to do.

If the above is too complicated, you could use something like nextdns.io, which would be like your “own cloud-based DNS”. It does logging too, so you can achieve the same without the “complexity” of setting up a DNS resolver.

BTW just googled a bit and found this: https://github.com/AdguardTeam/AdGuardHome/issues/244

It’s your problem, but with adguard instead of cloudflare. Problem is (was?, issue is from 2018) on side of TP-Link. You may have to update your firmware (your turn to laugh :), or (more likely) live with it…

I switched to 1.0.0.2 and problem is gone. It looks like 1.1.1.1 & 1.0.0.1 are not working for some reason.
Any ideas?

I don’t have Pi.

Not sure why I need to setup nextdns?

Yeah, updated my firmware to latest version avaliable already.

I never this problem before with Cloudflare. It started in 2020.

The suggestion of using a raspberry pi (or whatever other computer on your network) or nextdns (to do the same but remotely) was to be able to identify which DNS query your router does in order to verify whether you are connected or not.

Apparently your router has a problem using 1.1.1.1. It probably thinks it’s not a valid and/or non-public address. Unfortunately many devices think so, or even decide to “own” 1.1.1.1 as if it was a private address.

I have no idea, because I cannot know what your router tries (hence the suggestion of using a local/cloud resolver, but hey…). If 1.0.0.2 works, then problem solved, I guess. (AFAIK 1.0.0.2 is a testing address but may become official, who knows).