I just created a free EC2 instance with all the defaults. It says it's running in the AWS Management Console. On the "Instance Actions" menu, I click "Connect". I copy the DNS name provided (looks like ec2-a-dashed-IP-address.compute-1.amazonaws.com) and try to SSH to it. No response. I can't even ping it. What gives?
Apparently the default firewall is locked down, even though it doesn't look like it. Go to "Security Groups" on the left-hand pane of the AWS console, and select the "default" group. There are already entries for all TCP,UDP, and ICMP from a Source of "default group".
For a new entry at the bottom, select "SSH" from the "Connection Method" dropdown. The Source will default to "0.0.0.0/0" instead of "default group". Click "Save" over on the right and now it should respond when you try to SSH in.
If you want to ping it, create a similar new entry with protocol "ICMP", leaving the Connection Method as "Custom..."