I have installed and configured EC2 instance with routerOS which I want to use as main point of connection for branch networks. It has 1 interface, resides in subnet 172.20.1.0/24. Subnet 172.21.1.0/24 created within same VPC and has route tables as below: 172.20.1.0/24 - local 172.21.1.0/24 - local 0.0.0.0/0 - eni-xxxxxxxx (interface of routerOS in 172.20.1.0/24)
routerOS instance has elastic IP and works as router. Tunnel to branch configured and works well. Any AWS instance in any subnet reachable from any endpoint in branch network, but not vise-versa. I can't reach anything in branch from AWS VPC. The only instance reaching branch is routerOS itself. Security groups for both networks allowing all traffic from 172.20.0.0/16, 172.21.0.0/16 and 192.168.0.0/16 (branch subnets).
What am I doing wrong in this setup?
Solution was very simple. Disabling source/destination check in AWS adapter options made it work.