Serv-U How to block file share logins from outside of internal network

I am running version 15.1.2.189 and everything is setup. I have the Gateway in a DMZ and it's talking back to my Serv-U server on the local LAN.

For security reasons (don't want people brute forcing against the login page) I don't want the allow access to the Serv-U file sharing login page outside of my internal LAN.  However, I of course want to make sure that access to file share links still work outside of my LAN.

(My users will always be accessing their share links from within my LAN.)

I have tested a few options under the IP  Access tab, but it seems if I limit access to only my internal LAN ip range, that it also breaks access to the file share links from outside of my network.

Thanks for the help,

SB