Network interfaces is in use, cannot be deleted

Hi!

Please check out the documentation of Elastic Network Interface, there is a part regarding detaching and deletion of the resource:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html

Also please make sure to check out the "Description" field of ENI, you will find there information what this ENI was used for, for example:

• DMS: "DMSNetworkInterface"
• ElastiCache: "ElastiCache node-name"
• ALB: "ELB app/alb-name/auto-id"
• NLB: "ELB net/nlb-name/auto-id"

Sometimes time may be the issue as well - if you have deleted the load balancers, IPs etc., you might wait a little until ENI updates itself and you should be able to delete it.

First of all, if you created the resource using eksctl create cluster, you should attempt cleanup using eksctl delete cluster command.

At the minimal you might want to delete the CloudFormation stack, instead of manually delete resources.

That said, if the only issue you face as of now is the ENI cannot be detached, you can force detachment using the --force option of the detach-network-interface CLI command, refer here.

Lastly, you should provide feedback to Udemy course instructor for better clean up instructions. And AWS has it's free (you still need to pay for the resource usage) workshops here.

The easy path for this is, go in the console to EC2, then to Elastic Network Interfaces, and next to every interface you will find which service is using it, so delete the service and the ENI will fly away.

Best,