Can't see all computers on remote desktop

I have OS X Yosemite Server running on a fixed IP with a domain name and connect remotely by VPN. I use Remote Desktop to login to check the computers on the network. From some locations I can see all the computers fine. The network range is from IP 10.0.1.4 to whatever higher DHCP address they get assigned. This works great. However, from other remote locations I see only the server computer. What am I doing wrong here and why does it change based on where I am? My goal is to always see all the computers on the network regardless of where I VPN from.