Attach Elastic IP to EC2 Instance

🎯 Objective

Assign a static public IP (Elastic IP) to an EC2 instance so it remains reachable even after stop/start.

🧠 What is an Elastic IP?

An Elastic IP (EIP) is a static IPv4 address provided by AWS.

Key Points:

🏗️ How It Works

Internet → Elastic IP → EC2 Instance

👉 EIP is associated directly with the instance or its network interface (ENI).

🛠️ Method 1: Attach Elastic IP via AWS Console

📍 Steps:

1. Go to EC2 Dashboard

1. Click Elastic IPs (left sidebar)

1. Click Allocate Elastic IP address

1. Click Allocate

🔗 Associate Elastic IP

1. Select the allocated IP

1. Click Actions → Associate Elastic IP address

1. Choose:

1. Click Associate

⚙️ Method 2: Using AWS CLI

📌 Step 1: Allocate Elastic IP

aws ec2 allocate-address--domain vpc

Output will contain:

{
  "PublicIp":"3.x.x.x",
  "AllocationId":"eipalloc-abc123"
}

📌 Step 2: Associate with Instance

aws ec2 associate-address \
--instance-id i-1234567890abcdef0 \
--allocation-id eipalloc-abc123

🔍 Verify Elastic IP

aws ec2 describe-addresses

🔐 Allow Access (Security Group)

Make sure required ports are open:

Example:

Allow SSH:

port22 → your IP

Allow HTTP:

port80 →0.0.0.0/0

⚠️ Important Notes

📊 Elastic IP vs Public IP

🚀 Real Use Cases

🧪 Test Connection

ssh ec2-user@<elastic-ip>

🧩 Bonus: Disassociate / Release EIP

Disassociate:

aws ec2 disassociate-address--association-id eipassoc-xxxx

Release:

aws ec2 release-address--allocation-id eipalloc-xxxx

🧠 DevOps Tip

👉 Always use Elastic IP for production

👉 Avoid unused EIPs to prevent unnecessary charges