‘Knowing’ is not the same as ‘understanding’

Grrr… let this be a lesson: don’t assume that the error message returned knows what the problem is. The message ERR_INTERNET_DISCONNECTED may well not mean what it says.

Connection reset? Generally, that indicates a TCP issue at some link in the chain — and there are a huge number of links in that chain. But, let’s have a quick look at things: Internet is fine. Connectivity is fine. Things are working fine.

Maybe the browser can’t resolve that site.

How would we check?

Just ask DNS — DNS resolution in my network is every device forwarding to a single DNS node, which then forwards first to then to if the first one isn’t available. It will not switch between them unless a DNS server is unreachable.

I begin with an assumption that my resolver is fine. I tried a few generally unused hosts to see if they could resolve.

john:~ john$ dig @ one-confluence.pearson.com | grep -v "^;"

We also just have it throw out anything that begins with a semicolon, because at the moment, we don’t care. We only want to see the results. Hmm… nothing. Okay, let’s try the alternate resolver:

john:~ john$ dig @ one-confluence.pearson.com | grep -v "^;"
one-confluence.pearson.com. 126 IN CNAME one-confluence.glb.pearson.com.
one-confluence.glb.pearson.com. 29 IN A
Ah! Well, that's different.

A quick tweak to the router, and a refresh of the IP info on the workstation and…

Summary: yes, the errors mean things, but sometimes a developer jumps to their own conclusions.

Also, this tends to underscore that the two resolvers are not identical, nor are they expected to be.

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