AWS Security groups and AWS VPC Network ACLs are 2 solutions for controlling traffic in VPCs.

When rules in either deny an IP packet, do they REJECT or DROP (in the iptables sense)?

That is: are packets silently dropped, or does the firewall respond with a RST/ACK (tcp) or ICMP Port Unreachable packet?

1 Answer 1


I ran some experiments here: https://github.com/turtlemonvh/aws-network-experiments

Traffic denied by either AWS security group rules and network ACLs behaves identically to traffic encountering an iptables DROP rule (vs REJECT or REJECT --reject-with tcp-reset). No response is sent in either case.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.