Fundamentally, the F5 needs to be able to differeniate incoming traffic based on something unique, e.g. L7 information or IP address or port and from what I can gather you only have 1 Public IP (client side) that incoming traffic will hit and static ports to indicate which server is not really suitable for your setup. If the traffic was purely HTTP then the HOST header in the HTTP request has the DNS name of the service in it so the F5 can check the HOST header and route traffic to the correct server. But I'm assuming that there may multiple services other than HTTP that you want to use? If this is the case it is unlikely the F5 has any information available to it in the IP packets that indicates where this traffic should be destined, so it is possible as you've been told to setup a static mapping and use the port as a key to route traffic, i.e. port80->server1, port81->server2, although this may not be suitable for you, the only other alternative I can think of would be a public IP address per server.