Fix EC2 instance internet connectivity

It might be a case that you are new to AWS and you have recently launched a new EC2 instance. Now you are trying to update the OS using yum update or apt-get update but unfortunately, you are not able to do it because of an internet connectivity issue. Now you are stuck without any clue. things that you should try to fix the issue:

1. Verify Security Group Settings

1.1 Log in to AWS Management Console:

- Go to the EC2 Dashboard.

1.2 Select the EC2 Instance:

- Note the Security Group associated with the instance.

1.3 Navigate to Security Groups:

- In the EC2 Dashboard, select “Security Groups” under the “Network & Security” section.

1.4 Check the Inbound Rules:

- Ensure there's a rule allowing SSH (TCP Port 22) for Linux instances or RDP (TCP Port 3389) for Windows instances from your IP address.

1.5 Check the Outbound Rules:

- Ensure there's a rule allowing traffic to 0.0.0.0/0. Commonly, you should allow all traffic or at least HTTP (TCP Port 80) and HTTPS (TCP Port 443).

2. Check the Network ACLs (Access Control Lists)

2.1 Navigate to Network ACLs:

- Go to the VPC Dashboard and select “Network ACLs.”

2.2 Identify the Network ACL:

- Find the Network ACL associated with your instance’s subnet.

2.3 Verify Rules:

- Inbound Rules: Ensure traffic from 0.0.0.0/0 is allowed on necessary ports (e.g., port 22 for SSH, port 3389 for RDP).

- Outbound Rules: Ensure traffic to 0.0.0.0/0 is allowed on necessary ports (e.g., port 80, 443).

3. Verify the Route Table

3.1 Navigate to Route Tables:

- Go to the VPC Dashboard and select “Route Tables.”

3.2 Identify the Route Table:

- Find the Route Table associated with your instance’s subnet.

3.3 Check the Routes:

- Ensure there is a route directing 0.0.0.0/0 traffic to the Internet Gateway (IGW).

4. Check the Internet Gateway (IGW)

4.1 Navigate to Internet Gateways:

- Go to the VPC Dashboard and select “Internet Gateways.”

4.2 Verify IGW Attachment:

- Ensure that the Internet Gateway is attached to the correct VPC.

4.3 Confirm Route Table Association:

- Make sure the Route Table associated with the instance’s subnet is associated with the Internet Gateway.

5. Verify Subnet Configuration

5.1 Navigate to Subnets:

- Go to the VPC Dashboard and select “Subnets.”

5.2 Select the Subnet:

- Choose the subnet associated with your instance.

5.3 Check Auto-assign Public IP:

- Ensure that the subnet is configured to Auto-assign Public IPs if the instance needs a public IP address.

6. Reboot the Instance

6.1 Go to the EC2 Dashboard:

- Select the affected instance.

6.2 Reboot the Instance:

- Choose “Instance State” > “Reboot” to restart the instance.

7. Check the Instance’s Private and Public IP

7.1 Verify IP Addresses:

- Ensure the instance has an Elastic IP (if needed).

- Confirm that the instance’s private IP is within the correct range for the subnet.

8. Test Connectivity

8.1 After Rebooting:

- Attempt to SSH into the instance (for Linux) or use EC2 Instance Connect.

8.2 Test Internet Access:

- Try pinging a public IP (e.g., ping 8.8.8.8) or resolving a domain name (e.g., ping google.com) to verify internet access.

9. Check the Instance’s Network Interface (ENI)

9.1 Navigate to Network Interfaces:

- Go to the EC2 Dashboard and select “Network Interfaces.”

9.2 Verify ENI Attachment:

- Ensure the ENI is properly attached to the instance.

9.3 Check IP Addresses:

- Confirm that the ENI has the correct private and (if necessary) public IP addresses assigned.

By following these steps systematically, you should be able to identify and resolve most connectivity issues with your EC2 instance.