Thanks for the answer, PK.Unfortunately I wasn't clear enough. I was talking about outbound traffic from the server to the client (for example - server replying to client's request for web page). But your answer was clear. If both links are up, reply...

thanks for this nice trick. However,  what happens if both links are up, and a client access  web server via IP address of backup interface? What route will ASA use in this case? (Default route will point to ISP1, and client request will come through...