Exchange traffic b/w 3 security groups-CodePudding

I have 3 security groups. 1st security group "VPN security group", which I am referring in another security group calling it "private security group" and furthermore I am referring the "private security group" in "RDS security group"

I am unable to connect to the database through the "VPN security group" through the above setting.

But when I am referring the "VPN security group" directly in the "RDS security group" I can access the database.

Please let me know why the above setting is not working.

CodePudding user response：

This is because there is no transitivity between security groups. This means that when you accept traffic from "private security group" you are not accepting traffic from all the inbounds in "VPN security group". The only way is to reference "VPN security group" directly in "RDS security group".