Elastic IP address becomes unassociated with instance

Question

Hi,

So we have an EC2 instance setup with a load balancer and elastic IP....

It works perfectly, except when the Elastic IP address becomes unassociated with the instance.

The EIP addr is still there in the EIP table, just no instance is connected to it. 
And it does this seemingly at random. It will work for hours - days - then all of a sudden we can't connect. We check the EIP and it's unassociated. We re-associated it, and it's back to working again.  (We do not have the *Reassociation* checkbox marked when you go to associate an EIP, so that shouldn't be causing it.)

Other information:

1. No one has made changes to aws setting when it disassociates. 
2. It doesn't coincide with bitbucket pipeline build.
3. Security groups, inbound rules are still all the same and associated with the instance.
4.  We also only have a couple EIP, so we shouldn't be hitting any limits.

So we are at a complete loss. Nothing else seems to change in aws - just the EIP association.

Any ideas? I will happily add more information if needed.

Answer

Hello,

To check what could be disassociating the Elastic IP on the instance, you can use the CloudTrail tool. You may follow these steps:
[1] Open the CloudTrail console.
[2] On the left navigation pane, choose Event History.
[3] On the lookup attributes drop down list, choose event name.
[4] Enter DisassociateAddress as event name value.
[5] Choose the timestamp of when the occured.
[6] Then check the user agent that executed the API. The user agent will show the agent that disassoiated the Elastic IP.

You can also refer to the following document for more information regarding Cloudtrail event history: https://docs.aws.amazon.com/awscloudtrail/latest/userguide/view-cloudtrail-events-console.html#displaying-cloudtrail-events

Elastic IP address becomes unassociated with instance

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