Deep Dive into AWS Elastic IPs: Everything You Need to Know
Published: 2023-11-23 14:11:47

In the ever-expanding world of cloud computing, IP address management is crucial. Amazon Web Services (AWS) offers Elastic IP addresses (EIPs) as a solution for dynamic cloud computing needs. This blog post is a comprehensive guide on Elastic IPs in AWS, covering creation, attachment to EC2 instances, their advantages, disadvantages, use cases, and pricing.

## What is an Elastic IP (EIP) in AWS?

An Elastic IP (EIP) is a static IPv4 address designed for dynamic cloud computing in AWS. It's an address that you can allocate to your AWS account and associate with an EC2 instance or a Network Interface. Unlike traditional static IP addresses, EIPs allow for more flexibility and control.

### How to Create an Elastic IP

1. **Log into AWS Management Console**: Access the EC2 dashboard.
2. **Allocate New Address**: Under the “Network & Security” section, select “Elastic IPs” and then “Allocate New Address”.
3. **Choose Scope**: Decide if the EIP is for use within a VPC or EC2-Classic (if supported).
4. **Allocate**: Confirm to allocate the new EIP to your account.

[AWS Documentation on Allocating Elastic IPs](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html#using-eip-allocating)

### Attaching an Elastic IP to an EC2 Instance

1. **Select the EIP**: In the EC2 dashboard, under “Elastic IPs”, choose the EIP you created.
2. **Associate Address**: Click on “Actions” and select “Associate Address”.
3. **Choose Target Instance or Network Interface**: Specify the instance or network interface to associate with the EIP.
4. **Associate**: Confirm the association.

[AWS Documentation on Associating Elastic IPs](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html#using-eip-associating)

## Advantages of Using Elastic IPs

1. **Reliability for Reboot**: The IP address remains associated with the account until explicitly released, even through instance stops and starts.
2. **Reassociation Capability**: Quickly remap the address to another instance in your account, aiding in fault tolerance.
3. **Masking Instance Failure**: Instantly reroute traffic to another instance in case of failure.

## Disadvantages of Elastic IPs

1. **Limited Availability**: AWS limits the number of EIPs you can have.
2. **Potential Costs**: While Elastic IPs are free when in use, AWS charges for unattached EIPs.
3. **IPv4 Limitation**: Only available for IPv4, not IPv6.

## When to Use Elastic IPs

1. **Hosting Websites**: For hosting websites where the IP address should remain constant.
2. **Remote Access**: Providing a static IP for remote access and administration.
3. **Failover Systems**: For failover mechanisms in high-availability setups.

### **Case Studies**
### **Case Study 1: High-Availability Web Hosting**

**Scenario**: A company hosts a critical web application that requires high availability. They need to ensure that the application remains accessible even if the underlying EC2 instance fails or needs maintenance.

**How Elastic IPs are Used**:

- The company assigns an Elastic IP to their primary EC2 instance hosting the web application.
- In case of failure or during maintenance of the primary instance, they quickly reassign the Elastic IP to a standby instance.
- This reassignment is almost instantaneous, ensuring minimal downtime and maintaining the application’s availability.

**Benefits**:

- Provides a seamless failover mechanism.
- Minimizes downtime for critical applications.
- Ensures consistent IP address for DNS and end-users.

### **Case Study 2: Migrating Between Instances for Performance Upgrades**

**Scenario**: An organization needs to upgrade their server for enhanced performance without changing the server's IP address, which their clients use to connect.

**How Elastic IPs are Used**:

- The organization allocates an Elastic IP and associates it with the current server (EC2 instance).
- They prepare a new EC2 instance with upgraded resources.
- Once ready, they disassociate the Elastic IP from the old instance and associate it with the new instance.

**Benefits**:

- Allows for hardware upgrades without impacting IP address-dependent configurations.
- Reduces the complexity involved in notifying clients of IP address changes.
- Ensures business continuity during upgrades.

### **Case Study 3: Managing Geographically Distributed Servers**

**Scenario**: A business has servers in multiple AWS regions for redundancy and to serve a global customer base effectively.

**How Elastic IPs are Used**:

- The business assigns Elastic IPs to their primary servers in each region.
- In case one regional server goes down, they redirect traffic to servers in other regions by reassigning the Elastic IPs.
- This setup also allows them to perform regional maintenance without service interruption.

**Benefits**:

- Provides a robust disaster recovery strategy.
- Facilitates global load balancing and traffic management.
- Enhances user experience by reducing latency.

### **Case Study 4: Simplified Remote Access and Administration**

**Scenario**: IT administrators need consistent remote access to servers for maintenance and monitoring.

**How Elastic IPs are Used**:

- Each critical server is assigned an Elastic IP.
- Administrators use these static IPs for secure and consistent remote access, regardless of underlying instance changes.
- Elastic IPs also simplify firewall and security configurations, which can be IP-specific.

**Benefits**:

- Streamlines remote administration tasks.
- Offers stable connection points for secure access.
- Simplifies network and security management.

These case studies demonstrate the flexibility and utility of Elastic IPs in various operational contexts, highlighting their role in ensuring high availability, facilitating seamless migrations, managing geographically distributed infrastructure, and simplifying remote administration. Their strategic use can significantly enhance the resilience and efficiency of cloud-based systems.


## Pricing of Elastic IPs

Elastic IPs are free as long as they are attached to an instance and being used. However, AWS charges for EIPs under these circumstances:

- **$0.005 per hour** for each EIP that is not associated with a running instance.
- Additional charges if more than one EIP is associated with an instance.

[AWS Pricing Details for Elastic IPs](https://aws.amazon.com/ec2/pricing/on-demand/#Elastic_IP_Addresses)

## Conclusion

Elastic IPs are a powerful feature in AWS, offering flexibility and reliability for addressing in the cloud. While they come with limitations and potential costs, their benefits in certain scenarios, like maintaining a static IP for critical applications and failover systems, are invaluable. Understanding when and how to use them effectively can greatly enhance your AWS experience.

Remember to review AWS documentation and pricing details regularly, as AWS updates policies and pricing models over time. By doing so, you can make informed decisions and utilize Elastic IPs to their fullest potential in your cloud architecture.