Hi Chris,
Assuming Direct Access is setup correctly, it functions almost identically to a VPN solution. This means IP addressing, routing, etc. has to be 100%.
That being said, we typically do not recommend running Sage 100 over any type of VPN due problems with latency, MTU (packet sizes), how network drives handle VPN's (Sage Standard), and the general quality of WAN links. Even if a WAN link was a full 100megs, the overhead from the VPN will drop its throughput.
We find a terminal server solution performs much better since any type of disconnect will affect the terminal server session (screen updates only), but not disconnect the MAS client from the server.
Best regards,
Chris