SSH-proxy and keyboard interactive authentication not working

I believe I got it working now. Instead of using the public key on the backend server placed in /etc/ssh/ssh_host_rsa_key.pub, I used the public key that was in my clients .ssh/known_hosts, after having connected directly to 10.128.10.128. This key I placed in the Real Server Auth Public Key field and now I can log in, through the Bigip, using username/password and SCP is not allowed through, which was my goal.