Networkwifi
I am trying to find out my public IP address for my MacBook Air It is on Comcast/Xfinity Wifi (my parents had some tech dudes set it up). When I check http://ipecho.net or any other I get 73.170.168.215, but this is the same as on my iPhone 8.
On the contrary, the two devices have different local ip addresses with all the numbers the same except the last one 192.168.40.XXX. Is the public IP address the same thing as the router?
The airport settings go by location, not which of the possible SSID you join, so make a home (or Jensen) location and use manual IP or DHCP with manual address to get things going.
Check your firewall as it can block DHCP responses, but I'd guess the router has issues before the Mac, but something is broken for it not to just work.
Ah, it seems that the problem is that while "Internet Sharing" is ON, OSX does not instantiate the child connection (in your case, the WiFi network) until you actually get an internet connection on the parent connection.
You can potentially fool it with a loopback adapter on your ethernet connection (and perhaps static addressing and setting the router as itself), but I have not tried it.
Best Answer
It says here that you may need to setup port forwarding to allow incoming connections from port 15151 to your Mac. If your dad lets you, you may be able to try this in the router settings.