SecurityGroup

TL;DR¶

• essentially is a L7 firewall.
  • Stateful, if traffic is allowed out its allowed back in
• Locked down to a region /VPC combination.
• One SG can be attached to multiple instances.
• All inbound is blocked by default.
• All outbound allowed is authorized by default.
• SG can reference another SG in Inbound or outbound rules.
• Authorized IP ranges.

Troubleshooting¶

• timeout → SG issue.
• Connection refused → application or server error.

Best practice¶

• use separate SG for SSH access.

Classic ports to know¶

• 22 = SSH (Secure shell)
• 21 = FTP (File transfer protocol) to upload files into a file share
• 22 = SFTP (Secure file transfer protocol)- upload files using SSH.
• 80 = HTTP – access unsecured websites
• 443 = HTTPS - access secured websites
• 3389 = RDP (Remote Desktop Protocol) - log into a windows instance