Smart/RG SR400ac - this is the router/modem and connects to the outside Internet. The only device plugged into it with an ethernet cable is a Netgear R6900P router.
The Smart/RG uses 192.168.x.x, and the R6900P uses 10.0.x.x for internal addresses.
The Smart/RG forwards port 80 to the R6900P, which then forwards port 80 to the webserver. The webserver is plugged into the R6900P with an ethernet cable.
Both the Smart/RG and the R6900P have wifi.
If I try to access the website by domain name from outside of this network (public wifi, a wired computer at someone else's house, etc.) I can get to it with no issues.
If I try to access the website from ethernet-connected devices that are plugged into the R6900P, they can connect with no issues.
However, if I try to connect to the website using the wifi on either the Smart/RG or the R6900P using either the domain name or the IP address, it tries to log me in to the Smart/RG router's login page.
I can't figure out why I get the router's login page - if it's a setting on the Smart/RG, the R6900P, or the apache configuration on the webserver. Maybe it's some kind of race condition?
I realize this is a lot of information. Please ask any questions you have!