I have been experimenting with NACL and created a test EC2 instance (with Apache http server) in a public subnet. I restricted inbound and outbound to Port 80 and I wasn't able to access test page.

Question

What could be the reason for this?

Answer 1

You should open ephemeral ports (1024-65535) as your server will receive requests on 80 but send the response over one of those ephemeral ports. Blocking outbound for the ephemeral ports is blocking the response itself

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Comments

Thanks a lot!