This is a step by step guide on how to do LAN routing on this router model. This may work with other models and I am posting due to not being able to find it anywhere else and the absolute pain it was to discover. This may work on similar models.
Router info: D Link 850L, A1, FW: 1.12
This was done on google chrome
Log into router page
Status - Routing (Look at these for reference to make sure it worked)
Advanced - Routing
Enter all your information and notice that you can only route to WAN
Right click "WAN(xxx.xxx.xxx.xxx)"
inspect
Drop down until you get to options (Text will say "WAN (xxx.xxx.xxx.xxx)")
Rename value: "WAN-1" to "LAN-1"
Save settings
Check Status - Routing
Enjoy
