Amazon EC2 instance unable to resolve host.

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I have a bunch of amazon ec2 instances. Three instances became unable to resolve a specific url. When I try curl <url>, those three instances say "curl: (6) Could not resolve host", while all the other instances are able to resolve the url and return the correct data. It's only that specific url, as well - all other urls work fine.

What could have caused this? I haven't changed anything on any of the instances, so it's not something I did. How do I find out why it happened?

Aug 23, 2018 in AWS by datageek
• 2,440 points
350 views

1 answer to this question.

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Here is my checklist of things you need  to verify. Are you sure you havent’t changed the following:

  • DNS Settings on the instance? (check with dig to see if name resolution is OK)

  • NACL rules on the subnet where your instance is running?

  • Security Group rules of the SG attached to your instances?

Check if you have made any changes.

answered Aug 23, 2018 by Archana
• 4,090 points

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