Which High Availability mode should be used for an application that cannot be SNATed?

Applications that cannot be SNATed require preservation of the original client IP address. In Avi Load Balancer, preserving client IP is mutually exclusive with SNAT, because the Service Engine must forward traffic without replacing the source address. VMware Avi documentation for Preserve Client IP describes specific requirements and caveats for non-SNAT traffic handling. For this model, the Service Engine Group must use Legacy Active-Standby behavior, where the Virtual Service is active on one Service Engine and failover behavior is predictable. Elastic Active-Active mode generally relies on distributed placement and typically uses SNAT for symmetric return traffic handling. Therefore, when an application cannot use SNAT and must preserve the client IP address, the correct HA mode is Legacy Active-Standby .