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This lesson explains AWS Elastic IP addresses: what problems they solve, how they work, pricing considerations, and key limitations. It covers the workflow for allocating and associating Elastic IPs and includes CLI examples for common operations.

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Why Elastic IPs exist

When you launch an EC2 instance into a public subnet, AWS assigns a public IPv4 address from Amazon’s pool (for example, 1.1.1.1). That automatically assigned public IP is not reserved for your instance — it can change if the instance stops, starts, or moves to another host. Because these ephemeral public IPs are not persistent, using them for long-lived endpoints results in operational problems: clients, DNS records, or integrations would have to track changing IPs. Elastic IP addresses solve this by giving you a static IPv4 address reserved for your AWS account. You can associate that address with an instance or a specific network interface (ENI), and the public IP remains stable across reboots, stop/start cycles, or instance replacement.
  • Allocate an Elastic IP to your AWS account.
  • Associate the Elastic IP with an EC2 instance or ENI.
  • If you need to perform maintenance or failover, disassociate and re-associate the Elastic IP with another instance — clients keep using the same public IP.
A slide titled "Elastic IPs" showing an AWS Cloud diagram with two servers. Server A has a red error/cross icon, while Server B is shown with an assigned Elastic IP (1.1.1.1).

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Practical uses

  • Static public endpoints: keep a fixed IPv4 address for services that require a stable IP (legacy systems, IP allowlists).
  • Simple failover: move the Elastic IP between instances in the same region to redirect traffic immediately.
  • Maintenance: assign an Elastic IP to replacement instances without changing DNS records.

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Pricing and charging behavior

AWS pricing is designed to discourage hoarding of public IPv4 addresses. Typical billing behavior is:
Keep in mind: AWS intends Elastic IPs to be used sparingly. If an Elastic IP remains allocated but unused (not associated), you will be billed a small hourly fee until you release it.
A slide titled "Elastic IP Pricing" showing an orange chip graphic with several IP slots (one highlighted green) and an arrowed label that reads "Additional IP charged per hour."

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Important limitations and region behavior

  • Region-specific: Elastic IPs are allocated per AWS region. You cannot move an Elastic IP between regions.
  • Source pool: Elastic IPs may be from Amazon’s AWS-owned IPv4 pool or from a custom BYOIP (Bring Your Own IP) pool that you imported.
  • Attachment targets: Elastic IPs attach to instances or ENIs and map to the instance’s private IP address.
  • Account scoped: Elastic IPs are associated with your AWS account; they remain allocated until you release them.
Elastic IPs are region-bound. If you need global static addressing, consider using an AWS-managed service such as Global Accelerator or using Route 53 with health checks and failover — Elastic IPs cannot be moved across regions.
A presentation slide titled "Elastic IPs" showing two colored cards: an orange card labeled "Specific to a region" with a location-pin icon, and a pink card labeled "Amazon's pool of IPv4 addresses" with the AWS logo. A small "© Copyright KodeKloud" appears in the bottom-left.

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Quick AWS CLI examples

Allocate an Elastic IP for VPC:
Associate an Elastic IP with an instance (use the AllocationId from allocate-address):
Disassociate an Elastic IP (use the AssociationId from associate-address):
Release an Elastic IP (use the AllocationId):

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Summary

  • Default AWS-assigned public IPv4 addresses are ephemeral and can change when an instance is stopped, started, or replaced.
  • Elastic IPs are static IPv4 addresses you allocate to your account and associate with instances or ENIs to maintain a persistent public IP.
  • Elastic IPs are region-specific and can be reassigned between instances in the same region.
  • AWS discourages unused Elastic IPs via small hourly charges when they are allocated but not associated, and for additional IPs attached to the same instance.

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