Ethernet only works with certain wiring setup

I have ethernet wiring in my house and currently I have it set up with my router in one room, with one port connected to the wall and another connected directly to my home server. The wiring through the wall connects to my desktop. Everything works great. I decided I wanted to swap the computers, hooking my server up to the wall and the desktop somewhere else. The issue is that the home server's ethernet port doesn't even light up when I plug in the same cable that the desktop was working on 30 seconds earlier. It doesn't work when I have the server on dhcp or when assigning it a static IP outside of the router's assignable ip range. What could cause one ethernet port to be perfectly fine in one setup and another not even get a signal in the exact same setup?

Edited by hamluis, 14 August 2010 - 04:24 PM.
Moved from Internal Hardware to Networking forum ~ Hamluis.

If the server connection is gigabit and the laptop is 100Mbps the cabling could be the problem. 100Mbps only uses 2 pair of the four for communication where gigabit uses all four pair. incorrect wiring can cause the gigabit not to work. you can get cheap testers that will test the wiring is correctly landed. Wiring must also be CAT5E for gigabit to work properly.

CAT 6 would be better suited for gigabit. But ether way, the input wouldnt matter, its the same size, and ethernet doesnt power things, its data transfer, it would just be stuck at 100mb rates.

Your saying you have RJ-45 connections in your wall? where is the modem, or whats feeding your house with internet?

From those Rj-45 ports in the wall, you run an ethernet cord to a desktop, and the internet works.

BUT, when u swap the desktop to your server, the connection doesnt work?

Do i understand correctly?

Thanks...I should have the wiring needs to be AT LEAST CAT5E for gigabit.

You may have a situation where the wiring in the wall was installed with a crossover (one end EIA568A and the other 568B) and the desktop has auto-MDX while the server doesn't. Try using an ethernet crossover cable between the server and the wall (or check the current cable to make sure it isn't one). If you hold the RJ45 with the latch down the pins to the left should be white/green green for 568A and white/orange orange for 568B. If they are different on each end you have a crossover cable. There is a nice drawing here of the respective pinouts.