Sorry, I don't know how to force to use the IP number.
I am not an expert in networks, but in my case I try to avoid using numbers. The reason for that is that numbers sometimes change and that can cause a lot of problems cause you have to redirect after change. We have some problems once when our map editors use connection with numbers instead of name and after change it took us a lot of time to redirect everything. I think names are easy to handle and more stable, even you can do some manipulation local in each machine using the host file.
Sorry I can not help you.
Regards, Manuel