AWS Elastic IP Training Summary

Elastic IP (EIP) is a static IPv4 address designed for dynamic cloud computing in AWS. It is a reserved public IP address that you can assign to an EC2 instance and remap to other instances as needed.

Key Points

• Elastic IP Usage: Elastic IPs are used when a constant public IP is necessary. They are particularly useful for:
  • Masking instance or software failures by quickly remapping the IP to another instance running the same software.
  • Ensuring that certain applications or services that rely on a fixed IP address remain accessible.
• Billing: Elastic IPs are free as long as they are attached to an EC2 instance. However, if they are reserved but not associated with an instance, you will incur charges.
• Limitations: By default, AWS accounts are limited to five Elastic IPs. You can request more if necessary, but AWS encourages the use of alternative methods such as DNS names or Load Balancers.
• Alternatives: Instead of using Elastic IPs, consider:
  • Using a random public IP and registering a DNS name with Route 53.
  • Utilizing a Load Balancer, which provides a static hostname and can redirect traffic to the correct EC2 instance.

Hands-On Demonstration

1. Security Group Setup: Ensure the security group allows SSH access from any IP.
2. EC2 Instance Setup:
   • Create two EC2 instances, each with a unique file (hello-instance-1.txt and hello-instance-2.txt) to identify them.
3. Elastic IP Allocation and Association:
   • Allocate a new Elastic IP from Amazon's pool or use your own.
   • Associate the Elastic IP with the first EC2 instance.
   • Verify that the instance's public IP matches the Elastic IP.
4. Elastic IP Remapping:
   • Disassociate the Elastic IP from the first instance.
   • Associate the Elastic IP with the second instance.
   • Verify access to the second instance using the same SSH command, which now points to hello-instance-2.txt.
5. Cleanup:
   • Terminate the second instance.
   • Disassociate and release the Elastic IP to avoid unnecessary charges.

Conclusion

Elastic IPs provide a powerful way to maintain a consistent public IP address for EC2 instances. However, they should be used judiciously due to potential costs and the availability of other AWS services that can provide similar functionality.

I hope this session was informative, and I look forward to our next lecture.