Is it possible to detach Primary ENI for the EC2 instance?

Hello.

Please try removing the public IPv4 using the steps introduced in the URL below.
https://repost.aws/questions/QUVmpO9BWGSuGwQh5tXk3f5w/how-to-remove-ipv4-public-ip-address-from-ec2-instances-before-february-2024-ipv6#ANIgCHiXgQSdSiHc1wgH-6fA

I just following steps to complete

1. Create a new NIC and attach to the existing EC2 instance
2. Create a new EIP and associate with newly created NIC
3. As of now, Im having two private IPs and one Public IP that is EIP
4. Then I disassociate the EIP
5. I had a quick look at the EC2 instance - Now new dynamic IP has been appeared to the existing EC2 instance
6. I cant able to make disappearning Public IP from EC2 dashboard

Am i missing anything?

Hello! Given that you have resources that are IPV4 and IPV6 your VPC must be operating in dual-stack mode -- your resources can communicate over IPv4, or IPv6, or both. Your intent to transition your resources currently communicating on IPV4 to IPV6 only is not possible. https://docs.aws.amazon.com/vpc/latest/userguide/vpc-migrate-ipv6.html#vpc-migrate-ipv6-cidr Your intent to detach a primary network interface from an EC2 instance is not possible. You can create new ENIs and attach the ENI as a secondary network interface. https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html#eni-basics

My question - Is it possible to change the IPV6 for all the existing EC2 instances without providing any public IPV4 address? If yes please do let me know the solutions? (Without stopping - Because all of my EC2 instances are in Hibernated state) Yes you can change IPV6 addressing on existing EC2 instances without providing a public/elastic IPV4 address. https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/MultipleIP.html#working-with-multiple-ipv6

If you require IPV6-only I suggest creating IPV6-only subnets to launch your resources in. If you create an IPv6-only subnet, be aware of the following. An EC2 instance launched in an IPv6-only subnet receives an IPv6 address but not an IPv4 address. Any instances that you launch into an IPv6-only subnet must be instances built on the Nitro System. https://docs.aws.amazon.com/vpc/latest/userguide/create-subnets.html