Release Idle Elastic IP Addresses

Elastic IP addresses (EIPs) that are allocated but not associated with running resources incur hourly charges. This recommendation identifies idle EIPs that can be released to reduce costs.

What Are Elastic IPs?

Static IPv4 addresses for AWS resources that allow you to:

• Maintain consistent public IPs across instance replacements
• Quickly remap IPs to different instances
• Mask availability zone failures

Common Causes

1. Terminated Instances: EIP not released when EC2 instance deleted
2. Testing/Development: Allocated for testing and forgotten
3. Infrastructure Changes: Old IPs from decommissioned services
4. Deleted Resources: EIPs from removed NAT Gateways or Load Balancers

Detection Method

Uses AmazonVPC billing data for idle addresses:

• Service: AmazonVPC
• Usage Type: PublicIPv4:IdleAddress
• Criteria: Idle 7+ days

Cost Impact

Recommended Actions

1. Verify EIP Status

aws ec2 describe-addresses --allocation-ids eipalloc-xxxxxxxxx

Check output:

• InstanceId: null → Safe to release
• InstanceId: i-xxxxx → Still in use, don't release
• NetworkInterfaceId: eni-xxxxx → Check if ENI is attached

2. Check Dependencies

Before releasing, verify the EIP is NOT referenced in:

• DNS A records
• Firewall allowlist rules
• Application configurations
• Documentation

3. Release the EIP

AWS Console:

1. EC2 → Elastic IPs
2. Select unassociated EIP
3. Actions → Release Elastic IP addresses

AWS CLI:

aws ec2 release-address --allocation-id eipalloc-xxxxxxxxx

4. Update References

After release:

• Update DNS records (if applicable)
• Remove from firewall rules
• Update documentation

Important Considerations

Do NOT release if:

• Referenced in DNS (update DNS first)
• In firewall allowlists (update rules first)
• Reserved for disaster recovery
• Actively used (verify association status)

Recovery: You cannot recover the same IP once released. You must allocate a new one and update all references.

Best Practices

1. Tag all EIPs:

   Bash

   aws ec2 create-tags --resources eipalloc-xxx --tags \
     Key=Name,Value="Production API" \
     Key=Owner,Value=team-name

2. Regular audits: Review idle EIPs monthly in all regions

3. Automation: Set up Lambda to alert on idle EIPs detected

4. Use alternatives when possible:

   • Auto-assigned public IPs (free)
   • Application Load Balancer (AWS-managed IPs)
   • CloudFront (global edge network)

Cost Optimization

• Multiple EIPs per instance: First is free when associated, additional cost $3.60/month each
• NAT Gateway vs Instance: NAT Gateway has no EIP charges (included)
• Load Balancers: ALB/NLB don't require EIPs, often cheaper at scale