RAX120

Are you using the RAX120 or the RAX200? your title and signature have different models.

What modem are you using? Many times you get this issue if you've got multiple routers on the network. its called a double nat. 

https://kb.netgear.com/30186/What-is-Double-NAT

the 2 easiest routes to fix it are to either place the modem/router in passthrough/modem only mode or the other method is to place the router in AP (access point) mode.

> [...] When I go to http://www.routerlogin.net, I receive a notice that
> I need to be connected to the Router's WIFI network. [...]

   Welcome to what may be the worst error message in the world.  For an
explanation, try:

      https://community.netgear.com/t5/x/x/m-p/1365830

   Briefly, the idea is that "[www.]routerlogin.net" (or ".com") should
point to your own router, but that's true only if you use your own
router for DNS name resolution.  (Or, if the Netgear router can
intercept your DNS queries.)  Regardless, you should be able to get to
the thing using its IP address, if you can determine (or guess) that.
Normally, that would be something like "192.168.1.1" (for a plain
router) or "192.168.0.1" (for a modem+router), but it could be
different. ("10.0.0.1" is a typical alternate, for example.)

   General advice: An accurate quotation of an actual error message is
often more useful than an interpretation of an actual error message.
Usually works better in a Web search, too.  Copy+paste is your friend.