I have 2 xboxs going to 1 splitter not workin

I have 2 xboxs and 1 splitter [Netgear(IDK the model but it has 5 ports)] and i have 2 xboxs both hardwired. The one upstairs works like a charm. But when I go downstairs to play on that one it doesn't work. It isn't the ethernet cable (even though both xboxs are not connecting downstairs) because my dad has tried his computer with the ethernet cable and it read the internet in a zip. I have already taken off the firewall for my downstairs and that worked for 10 minutes then it stopped. I need help!

-Sincerely

Dangerdug (xbox live gt)