Inability to ping and connect to instance via SSH

0

Hello, I've created successful multiple instances in EC2 with correct network parameters (ports 22, 80 and 443 open), but unfortunately I still cannot connect or ping to the VMs, even if I have created public DNS and IP. I think this is a problem regarding my account and not the configuration. Any help will be kindly appreciated!

  • Review Key Pair: If you're using SSH key pairs for authentication, make sure you have the correct private key and that it has the appropriate permissions (e.g., 400).

Dimpep
asked 21 days ago144 views
2 Answers
1
Accepted Answer

Hi,

The best way to connect to EC2 instances initially is to use Instance Connect: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-connect-methods.html#ec2-instance-connect-connecting-ec2-cli

This tutorial is good: https://www.youtube.com/watch?v=lxSNeF7BAII

If your setup doesn't work this Knowledge article will help you debug it: https://repost.aws/knowledge-center/ec2-instance-connect-troubleshooting

Finally, when Instance Connect works, you can get back to a remote ssh from your laptop.

Re ping, be aware that it is ICMP protocol and not TCP: so, you need ICMP rules in your security groups to be able to ping. See https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/security-group-rules-reference.html#sg-rules-ping

Best,

Didier

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answered 21 days ago
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  • I have done everything right. From the biggest to the smallest detail. And still doesn't work, either by SSH or via Instance Connect. Ports are open, public IP and DNS are active, it supposed that my linux distro will have the instance connect pre-installed. and still I can't connect

  • Hi, first thing: check that your distro is supported by InstanceConnect : see https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-connect-prerequisites.html#eic-prereqs-amis

    BTW, which distro do you use?

    I strongly recommend that you get it to work with InstanceConnect before anything else. Also, if it is your first time, I strongly suggest that you do it with the default Linux instance (AL2023) proposed by EC2 instance creation wizard. This way, you'll be on solid ground to understand how it works.

1

First off, check if your instance has a public IP address assigned. Just head over to the AWS Management Console, find your instance, and peek into its details.

Now, let's double-check that Public DNS. It should look something like ec2-... ... ... ... .compute.amazonaws.com. Make sure it's all set up and ready to go.

Next up, those security groups. We want to make sure they're allowing inbound traffic on ports 22 (SSH), 80 (HTTP), and 443 (HTTPS) from 0.0.0.0/0. But hey, remember, opening up to the whole world isn't usually the best idea for security reasons.

Take a look at your instance's subnet. Is it in a public one? Public subnets have a route to an Internet Gateway, which is essential for internet communication.

Now, those NACLs. They usually allow all traffic by default, but just give them a once-over to make sure nothing's blocking outbound traffic from your instance.

Lastly, let's put your instance to the test. Try pinging or curling some public endpoints from the instance itself. If everything's set up right, you should be good to go!

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  • Dimpep, Note you can’t ping an EC2 without allowing ICMP on the security group and NACLs either.

  • I've done everything as you suggested and still can't access the instance. How can I test connectivity from the instance itself?

  • I can't even connect using Instant Connect. The error message is the following Failed to connect to your instance EC2 Instance Connect is unable to connect to your instance. Ensure your instance network settings are configured correctly for EC2 Instance Connect. For more information, see EC2 Instance Connect Prerequisites at https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-connect-prerequisites.html.

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