BGP Asymmetric routing when using ASA with AWS
When you have redundant VPN connections to AWS using a Cisco ASA, and you have configured BGP routing, asymmetric routing will typically take place. Communication that is sent out via one tunnel is responded to via the other.
The ASA is configured to drop responses that arrive asymmetrically by default.
There are several solutions that have been successfully applied, although the best approach is to discuss your requirements with AWS staff.