Elastic IP in AWS (Your Permanent IP Address)

Introduction 🚀

When working with AWS, maintaining consistent public IP addresses for your cloud resources is crucial—for example, to ensure reliable connections for web servers, VPNs, or other internet-exposed applications. This is where Elastic IP (EIP) comes into play.

In this post, we’ll explore:

• What an Elastic IP is
• Why it’s important
• How to allocate and manage an EIP with examples

What is an Elastic IP? 📬

An Elastic IP (EIP) is a public IPv4 address that you can associate with AWS resources, such as EC2 instances or NAT Gateways. Unlike regular public IPs, EIPs are static, meaning they remain the same unless you explicitly release them or associate them elsewhere. This provides a permanent IP address for your system/instance.

Elastic IPs help you maintain persistent connections to your resources, even if the underlying instance changes or restarts.

Key Features of Elastic IP

• Static Public IP: The IP remains unchanged even if the instance reboots.
• Re-mapping Flexibility: You can switch the EIP between multiple resources to ensure continuity.
• Fault Tolerance: If an instance fails, reassign the EIP to another healthy instance to minimize downtime.
• 1-to-1 Mapping: Each EIP can be associated with one instance or resource at a time.

Real-Life Example of Using an EIP 🛠️

Let’s say you’re hosting a web server on an EC2 instance. If the instance restarts, it will receive a new public IP unless you attach an Elastic IP. This would disrupt your website because DNS entries or user connections rely on a static IP address.

Solution:

1. Allocate an Elastic IP in AWS.
2. Associate the EIP with your EC2 instance.

Now, even if your instance restarts, the public IP address remains the same. This is especially useful when:

• Hosting websites or APIs that require a consistent IP address
• Setting up VPNs that rely on whitelisted IPs
• Preventing downtime when switching to backup instances

Allocating and Associating an EIP – Step-by-Step

Here’s how you can allocate and use an Elastic IP in AWS.

Step 1: Allocate an EIP

1. Go to the EC2 Dashboard in AWS.
2. Click on Elastic IPs from the left menu.
3. Click Allocate Elastic IP Address.
4. Confirm the allocation by clicking Allocate.

Step 2: Associate the EIP with an Instance

1. In the Elastic IPs section, select the newly allocated EIP.
2. Click Actions → Associate Elastic IP Address.
3. Choose the instance or network interface to associate with the EIP.
4. Click Associate.

Step 3: Verify the Association

1. Go to Instances in the EC2 Dashboard.
2. Check if your instance now has the Elastic IP as its public IP address.

Pricing Considerations 💸

While Elastic IPs are free if attached to a running instance, AWS charges a small fee if:

• EIP is allocated but not associated with any instance.
• Multiple EIPs are allocated to the same account.

This ensures that resources are not wasted and encourages good cloud management practices.

EIP vs. Dynamic Public IP: What’s the Difference? 🤔

Real-World Analogy:

Think of an Elastic IP like a permanent phone number. If you change phones (EC2 instances), you can keep the same number (EIP), ensuring that people (users) can still reach you.

A dynamic public IP is like a temporary number—changing each time you restart your phone (instance), making it difficult to stay connected consistently.

Common Issues and Troubleshooting 🔧

• Elastic IP Already in Use: Ensure that the EIP is not associated with another resource.
• Cannot Associate EIP: Check if your instance is in the same VPC as the EIP.
• Charges for Idle EIP: Avoid leaving EIPs unassociated to prevent additional charges.

Conclusion 💡

Elastic IPs are a powerful tool in AWS for ensuring high availability and fault tolerance. They allow you to maintain a consistent public IP address across multiple instances and are essential for production workloads that require persistent connections.

Next time you deploy a web application or VPN on AWS, try using an Elastic IP to ensure uninterrupted service! But do not forget to release it if there is no current use, as it incurs charges if unused.

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