The resources on your AWS Account are connected to share information using the Virtual Private Cloud (VPC). An Elastic IP Address is a static public IPv4 address associated with your AWS account in a specific Region. Unlike an auto-assigned public IP address. An Elastic IP address is retained when you stop and restart your Virtual Private Cloud Instance (VPC). It can be associated with an EC2 instance at any time using one of the following tools. An EC2 Instance console, AWS CLI and AWS Tools for Windows PowerShell. In this article, you will learn how to fix Elastic IP Address Could not be Associated. Learn about how to Setup a Site-to-Site VPN Connection on AWS.
You may also be interested in this related guide on What to note: Assigning Multiple IPs’ to an Instance. To deep dive into how to allocate, associate, disassociate and release EIP. Refer to this related guide: on How to Allocate, Associate, Disassociate and Release Elastic IP Address from an EC2 Instance.
The primary function of an EIP
It is important to understand that the primary function of these IPs is to conceal the failure of software or instances in your AWS account. This is done by rebinding the address to another instance as soon as possible in your account. An IP address is automatically assigned to your AWS account and remains yours until you choose to release it.
On the other hand, you can specify the IP address in a DNS record for your domain. This ensures that the specified domain refers to your instance.
You can also review the following post to learn about working with EC2 Instances. How to create and mount FSx File System: Join EC2 instance to AWS Managed AD, how to Add and Format a New Virtual Disk to an EC2 Instance.
When is this Error Likely to Occur?
The error is likely to occur when trying to associate an Elastic IP Address to a running EC2 Instance. If you ever experienced the error “Elastic IP Address could not be associated“, this guide shows you the step-by-step guide on how to Fix the Elastic IP Address Could not be Associated error.
It is likely an error that can occur when trying to connect to your EC2 Instance that doesn’t have a Public IP Address associated with it and you need to associate an EIP.
The reason why your running EC2 instance might not have a Public IP Address attached is probably due to the fact that you had disabled the auto-assign IP Address to the instance when creating it.
The major cause of the error is that Internet Gateway is not attached to the VPC containing the EC2 Instance which you wish to associate the Elastic IP Address with. AWS Internet gateways which enable communication between your public subnets and the internet must be attached to a VPC before associating an Elastic IP Address with an EC2 Instance.
An AWS Internet Gateway is a VPC component that allows communication between instances in your VPC and the internet. It is redundant, horizontally scaled, and highly available.How to Attach Internet Gateway (IGW) to Elastic IP Address
It is believed that you have set up your VPC already. If you have not, refer to the quick steps in setting Up the AWS VPC post.
To attach Internet Gateway to Elastic Ip Address, take the steps below:
Step 1: Attach Internet Gateway. To attach IGW, browse to the AWS VPC dashboard and click on the Internet Gateways tab. Select the available Internet Gateway in your account and click on Action and then click on Attach to VPC.
Step 2: Select the VPC you wish to attach Internet Gateway to if you have more than one VPC and then click on Attach internet gateway as shown in the screenshot below.
Step 3: Check to see that the IGW has been attached as shown below.
Step 4: Re-associate the Elastic IP Address to an EC2 Instance. To re-associate EIP, navigate to the EC2 Instance dashboard, locate Elastic IP blade and click to reveal the already allocated EIP, then select it and click on Action and select “Associate Elastic IP address”.
Step 5: Pick the running Instance you wish to associate the EIP with and click on Associate.
The EIP should be successfully associated with a prompt message in green as shown below.
I hope you found this blog post helpful on how to fix Elastic IP Address Could not be Associated.. If you have any questions, please let me know in the comment session.