What does TP-Link "Test DNS Root" actually do?

Question

The TP-Link router I'm using has a section in the UI called "Diagnostic", and one of the tests performed as part of "Test Internet Surfing" is called "Test DNS Root". At the moment, all tests are passing apart from this one.

What does this test actually do?

I've tried two sets of DNS servers suggested by the ISP, and also the Google DNS servers, but that test always fails.

I'm using the following router on PlusNet, a UK ISP.

Model: TP-Link TD-W8970

Firmware: 0.6.0 2.9 v000c.0 Build 131114 Rel.33362n

Answer 1

TP-Link Diagnostic "Test DNS Root" fails. What does it actually do?

It would appear to be doing a Ping test using the DNS Root Server(s) as a target address.

One report suggests the target is actually www.root-servers.net which is a non-existent address.

There are lots of similar reports of this error from different TP-Link models with nothing to suggest an resolution that I could find.

Conclusion: Broken diagnostic code

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I think the "Test DNS Root - Fail" is just a broken test which always fails. The test being broken doesn't really matter and won't affect anything else. I think the test does a DNS lookup for www.root-servers.net, which doesn't seem to exist, and I'm not sure what the purpose of a test looking up that name could possibly be.

Source TP-LINK TD-W9980 replacing HH3

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Test DNS Root fails because the root DNS blocks Ping and it won't affect internet access although it shows Fail

Source TD w8980 diagnostics says DNS root fail