Running a CA Access Gateway (SPS) and 2 replicated in HA backend servers, how to set failover of the backend servers, so in case the backend server 1 is down, the CA Access Gateway (SPS) sends a request to the second backend server?
As per documentation, use a network device that will do the load balancing or failover (1).
There's no such embedded failover functionality for the communication with the backend server.
If there's a need to get the CA Access Gateway (SPS) to have embedded functionality for failover and load balancing of the backend server connections, open an Enhancement Request (Idea) (2).