You get a call from a customer saying: "I can ping my instance but can't connect (ssh) it". What might be the problem?

If you can ping an instance but cannot SSH into it, the issue is likely related to one of the following:

• Security Group Rules: The security group attached to the instance may not have a rule allowing inbound traffic on TCP port 22 (the default SSH port).
• Firewall on the Instance: A firewall running on the instance itself (like iptables or firewalld) might be blocking the SSH port.
• SSH Service: The SSH daemon (sshd) on the instance might not be running or could be misconfigured.
• Incorrect SSH Key: You might be using the wrong private key to connect to the instance.