Question 233564 in Amazon Web Sevices Question posted in
The official Amazon Web Services documentation can be found here.

Amazon web services – Ec2 instances Public IP – Where it is assigned?

I am still learning AWS so please bear with me. I tried searching google but couldnt get any precise answer to my question. I am a CCIE myself so networking is not new to me.

When we create new EC2 instance in default VPC every instance gets a Public IP and Private IP. Private IP is assigned to the ENI. Perfect. Where is the public ip assigned? how its done? i think it should be NAT behind the scenes right? or else how can you assign a Public IP without actually assigning it somewhere.

Please confirm my doubt

I tried to find the answer in aws documentation but couldnt find it

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2

Answers


  1. 0

    Amazon has it’s own pool of public ip addresses, which gets assigned to your instances based on where you deployed them.

    A public IP address is assigned to your instance from Amazon’s pool of public IPv4 addresses, and is not associated with your AWS account. When a public IP address is disassociated from your instance, it is released back into the public IPv4 address pool, and you cannot reuse it.

    See here: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-instance-addressing.html

    I’m not sure if you’re looking for a more in-depth answer.

    But something to be aware of, is that AWS will start charging you for all active and waiting public ip addresses, due to the shortage.

    See announcement: https://aws.amazon.com/blogs/aws/new-aws-public-ipv4-address-charge-public-ip-insights/

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  2. 0

    Behind the scenes, the public ip is VIP that is mapped to the private ip address using static nat.

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