What is stateful filtering in VPC

Question

Can someone help me with the stateful filtering in AWS VPC? Thank you in advance.

Answer 1

Stateful filtering is used to track the origin of a request and this can be used to automatically allow the reply to the request to be returned to the originating computer.

For example, a stateful filter that will allows inbound traffic to the TCP port 80 on a webserver will allow the return traffic, usually on a high numbered port to pass through the stateful filter between the client and the webserver.