Elastic IP

 

What is an Elastic IP in AWS?

An Elastic IP address is a static, public IPv4 address designed for dynamic cloud computing. It is associated with your AWS account, and you can allocate it to any instance within a particular region. Unlike traditional static IP addresses, an Elastic IP address can be dynamically remapped among your instances, allowing you to quickly recover from instance failures and reconfigure your applications without DNS changes.

Key Features:

• Static IP Address: It remains the same, allowing for consistent access.
• Flexible Reassignment: You can reassign it to different instances within the same AWS region, making it easier to handle instance failures.
• Elasticity: Provides better availability by allowing you to mask instance or Availability Zone failures by rapidly remapping your public IP addresses to any instance in your account.

Use Cases:

• Replacing failed instances: If an instance fails, you can quickly remap the Elastic IP address to another instance.
• Avoiding DNS changes: By using Elastic IP addresses, you avoid the need to update your DNS records every time you launch a new instance.

What is Reverse Billing in AWS?

Reverse billing in the context of AWS typically refers to a pricing model where charges are borne by the service provider rather than the service consumer. This concept is more common in telecom services where the called party pays for the call (reverse charge or collect call). In AWS, reverse billing isn’t explicitly defined, but the concept can loosely apply to scenarios like:

• Cross-Account Billing: Where one AWS account pays for resources used by another account, often managed through AWS Organizations.
• Cost Allocation: Assigning costs of shared resources to different departments or projects within an organization.

How Elastic IPs and Billing are Associated

1. Elastic IP Address Charges:

   • Free Usage: AWS provides one Elastic IP address associated with a running instance at no additional charge.
   • Chargeable Usage: You incur charges when:
     • The Elastic IP address is not associated with a running instance.
     • You have more than one Elastic IP address associated with an instance.
     • Elastic IP address remaps exceed 100 per month.

2. Reverse Billing Context:

   • In AWS, the account that owns the Elastic IP address is billed. This can be particularly relevant in scenarios where multiple accounts are involved, such as in a multi-account architecture managed through AWS Organizations.
   • Cost Allocation Tags: You can use cost allocation tags to track and allocate Elastic IP costs to different projects or departments within your organization, effectively implementing a form of reverse billing.

Example Scenario

Elastic IP Usage and Billing:

• You have an application running on EC2 instances that requires a static IP address for external communication. You allocate an Elastic IP address and associate it with an instance. If the instance fails, you reassign the Elastic IP to another instance to ensure continuity. AWS charges apply based on whether the Elastic IP is attached to a running instance or not.

Cross-Account Billing:

• You have a central AWS account managing networking resources, including Elastic IPs. Multiple AWS accounts under your organization use these Elastic IPs. The central account receives the billing, but costs are tracked and allocated to the respective accounts or projects using cost allocation tags.

By understanding Elastic IP addresses and their associated billing, you can manage your AWS resources more effectively, ensuring high availability and cost efficiency.