AWS Elastic IP vs Public IP » –

In this article Kevin will compare the difference between Elastic IP and Public IP. Elastic IP is a new concept when using AWS (usually AWS services are prefixed with E which means Elastic describing the meaning of service scalability and flexibility).

First of all, Elastic IP and Public IP are both public which means that you can assign them to an EC2 instance that you can access from the Internet. But EIP and Public IP have a lot of differences and as a Cloud Architect you need to understand how to use them.

Definition

  • Public IP: is the IP address assigned to the EC2 instance obtained from Amazon’s pool, not associated with your AWS account.
  • EIP: EIP allocation linked to your AWS account.

Cost

  • Public: Free
  • EIP: Free to use, charges will apply if you are not using, not linked to AWS resources, or in stopped state.

Attached IP per instance

Public: 1

EIP: more than one. but additional EIP will be charged.

Static or Dynamic

  • Public: Dynamic. Change when stop and start again.
  • EIP: Static. Keep even when you stop and start the instance again.

Limited per account

Public: Unlimited

EIP: 5

Can recovery

Public: No

EIP: may recover if no one request for it.

Share publicity

Public: not recommended. IP Address can be changed.

EIP: Yes

Public IP will be assigned if the EC2 instance you initialize has public access enabled, for EIP you need to request / allocate EIP and assign with EC2 explicitly. Note that you have an EIP per Region of 5 when creating workloads. You should consider using it in conjunction with ELB for a more flexible load-balancing architecture.

Have fun!

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