DNS Error after IP address reset

Question

Hello
We use a single EC2 Instance on AWS that hosts our ESRI ArcGIS Server. On this server we provide a number of REST endpoints (map layers) that are accessible in web-mapping applications by the public via the internet. Our EC2 instance was restarted yesterday. Once the instance was restarted the rest services can no longer be accessed. The ArcGIS Server and the rest services are still running and I can see them on the instance, however I am unable to access these via the internet. It would appear that our public IP address has changed after the restart - I receive an HTTP ERROR 503 when I try to access the site. As far as I understand this, the DNS server is unable to resolve the name, possibly because the IP address it is looking for has changed.

I am at a bit of a loss as to how to fix this on AWS and can't find any guidance. Can anyone advise what steps are required to correct this?

Thanks,
Peter

Answer

To keep a particular static IP address, what you will need to do is Assign an Elastic IP Address to the EC2 instance.
This is a fixed IPv4 address that you can reassign from one EC2 instance to another. This address stays persistent through instance stops and starts.

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html

Answer

Since you mentioned, 
> the DNS server is unable to resolve the name, possibly because the IP address it is looking for has changed.

I would recommend checking the Record entry for the DNS name in the hosted zone, if it's still using the old Public IP address then this could be the reason why the DNS resolution is failing.

If you are making use of Amazon Route 53, I would recommend checking the record details in Route 53 console and if outdated edit the A record to the new Public IP address [1].

Another recommendation would be to make use of of Elastic IP address to retain the Public IP address [2] which was assigned to the EC2 Instance. By doing so you would not be required to edit the record every time the EC2 reboots.

Reference:
1.  Elastic IPs: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html
2.  Editing Records R53: https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/resource-record-sets-editing.html

Answer

This issue has now been resolved. In the end it wasn't an issue with a changed IP address, but an outdated version of AVG antivirus that was blocking various processes from occuring. Thanks.

DNS Error after IP address reset

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