SSH login to ec2 instance is not possible

Based on your SSH connection timeout issue, there are several potential causes to investigate beyond just security group settings. Here's what you should check:

1. Network Configuration:

• Verify your VPC has an Internet Gateway attached
• Confirm the subnet's route table has a route to the Internet Gateway (0.0.0.0/0 pointing to the IGW)
• Ensure your instance is in a public subnet
• Verify your instance has a public IP address assigned

2. Security Settings:

• Double-check that your security group allows SSH (port 22) from your specific IP
• Verify Network ACLs allow both inbound and outbound traffic on port 22 (unlike security groups, ACLs are stateless and require rules in both directions)

3. Instance Status:

• Confirm the instance is in the "running" state and has passed all status checks
• Check the instance's system log in the EC2 console for any boot-time errors

4. Alternative Access Methods:

• Try AWS Systems Manager Session Manager if your instance has the SSM agent installed
• For Ubuntu instances, you may be able to set up an IAM role and connect using Session Manager

5. Troubleshooting Steps:

• Try connecting using the instance's public IP address instead of its DNS name
• Check if there are any OS-level firewall rules blocking incoming connections
• Consider enabling VPC Flow Logs on the network interface to diagnose traffic issues
• Try launching a new instance in a different subnet or region to isolate the issue

If you've verified all these settings and are still unable to connect, it might be worth trying to create a new instance to determine if the issue is specific to your current instance configuration.
Sources
Unable to SSH into AWS EC2 Instance – Connection Timed Out & Forgot Credentials | AWS re:Post
Unable to connect to EC2 instance. | AWS re:Post
Unable to ssh to an EC2 instance | AWS re:Post
Port 22: Connection Time Out Issue | AWS re:Post

Yes, is good information to understand.