An Elastic IP (EIP) is a static, public IPv4 address you allocate to your account and can attach to an instance — and re-attach elsewhere if that instance fails. It stays the same even when the underlying instance changes.
Why it matters
Regular public IPs on EC2 change when an instance stops and starts. An Elastic IP stays fixed and can be remapped to a healthy instance for quick failover. Note: AWS now charges for EIPs, and best practice is often to use a load balancer or DNS instead of relying on many EIPs.
Test yourself
An application needs a fixed public IP address that can be quickly remapped to a standby instance if the primary fails. What do you use?
- The instance’s default public IP
- An Elastic IP address
- A private IP address
- A NAT Gateway
👉 Click to reveal the answer & explanation
Correct answer: B. An Elastic IP is a static public address you can remap to another instance for fast failover. A default public IP (A) changes on stop/start; a private IP (C) isn’t internet-facing; a NAT Gateway (D) is for outbound access, not a remappable public endpoint.
Related topics
Amazon EC2 · Amazon VPC · Elastic Load Balancing
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