I have a very curious case that has dumbfounded me.

I was trying to get a certificate from letsencrypt and I was consistently getting errors that certbot is unable to validate the domain (I was using --webroot option).

I even tried placing a file in the .well-known directory to test it and I got very peculiar results. When using my browser to access the file I got the contents of the file... however when using wget http://myaddress.tld/.well-known/... I got a different page that I have never seen before.

What can be causing this case of two different results from the same web address?

closed as off-topic by Jeff Schaller, RalfFriedl, Isaac, X Tian, JigglyNaga Nov 20 '18 at 14:03

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions describing a problem that can't be reproduced and seemingly went away on its own (or went away when a typo was fixed) are off-topic as they are unlikely to help future readers." – Jeff Schaller, RalfFriedl, Isaac, X Tian, JigglyNaga
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  • 3
    different User-Agent – Ipor Sircer Nov 14 '18 at 7:02
  • Can't confirm you get the text file in a browser. If you have a login cookie set, the server could spot that even when you go through a proxy. – Ulrich Schwarz Nov 14 '18 at 7:18
  • @IporSircer what does this mean and how does it help me? – RandomWhiteTrash Nov 14 '18 at 7:40
  • DNS giving inconsistent answers for IPv4 and IPv6? – Isaac Nov 18 '18 at 21:59

I found the reason...

DNS had different physical servers in IPv4 and IPv6 records (A and AAAA) and one place (my browser) was using IPv4 while all the other servers I checked used IPv6, including certbot.

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