AWS not able to delete network interface

Question

In AWS, i have network interfaces, which i am not able to delete, because they are supposedly in use. I have tried detaching them by the force option, but that deid not work.

How am i able to identify the object the network interface uses?

Answer 1

The best way to find the resource which a network interface is attached to is checking the 'Description' field of the ENI.

Depending on the resource type this Description field could change. Some examples I get from my environment are:

• DMS: "DMSNetworkInterface"
• ElastiCache: "ElastiCache node-name"
• ALB: "ELB app/alb-name/auto-id"
• NLB: "ELB net/nlb-name/auto-id"
• Nat Gateway: "Interface for NAT Gateway nat-id"
• Transit Gateway Attachment: "Network Interface for Transit Gateway Attachment tgw-attach-id"
• RDS: "RDSNetworkInterface"
• EC2 Instance: "Primary network interface" or can be empty too. For this resource type the fields 'Instance details' contains the information.
• VPC Endpoint: "VPC Endpoint Interface vpce-id"
• Lambda: "AWS Lambda VPC ENI-lambda_name-id"
• ECS Task: "ecs-attachment-arn"
• etc

So checking the value of this field you can identify on most case the resource which use that ENI.