Solved Trouble with house-wired ethernet in some rooms, but not others

[namtraab]

I live in a newly constructed home that was wired with ethernet cables throughout. The current internet setup is: ISP modem to wireless router (ASUS RT-AC68U) with ethernet cables running from the router to a "board" (I'm not sure what it is properly called) that connects to 8 ethernet cables that run throughout the house to various rooms. Most of our device run on WIFI (which works perfectly fine), so there are only a couple connections from the router to the board. Recently, I wanted to hook up a desktop computer (which doesn't have WIFI) via ethernet in one of the rooms, but ran into problems. I will try to describe the scenario as best and clearly as I can:

I will call the room that is having problems "Room A". I have been trying to connect using two computers. One is the above-mentioned desktop ("Desktop") and the other is a laptop ("Laptop") that I've used for diagnostic purposes. The Desktop runs Windows 7 Pro and the Laptop Windows 7 Ultimate.

In Room A, I connect the Desktop to the wall ethernet connection, which is wired through the house as described above (so I use two movable ethernet cables in total: one from router to board, one from wall socket to computer). The desktop does not get an internet connection, instead it has the yellow exclamation marker over the icon. If I then try the Laptop in Room A with the same cable setup, I connect to the internet just fine (I am not using wifi for these tests). So something seems wrong with the Desktop.

Then, I move the Desktop to another room ("Room B"), served by a different ethernet cable wired in the house. Using the same two ethernet cables I used for the Room A setup, I connect the Desktop. It connects to the internet just fine! So the desktop at least has to ability to connect to the internet. The Laptop also connects just fine through the ethernet in Room B.

So the Desktop works in Room B, but not Room A. The Laptop works in both Room A and B. (I have also done this test with a second laptop computer running Windows 7 Home Premium, and it has the same problem as the Desktop, but other than that provides no more new information.) Overall, the only different between the Room A setup and Room B setup is the hardwired house ethernet cable. But if that cable is bad, why would the Laptop still be able to connect via ethernet?

From an "ipconfig /all" of the Desktop in room A, I see that the IP address is a 169.254.x.x one, which isn't what it should be based on my internet searches (something about APIPA and possible DHCP problems). When the Desktop was in Room B, it didn't have this. I then set the router settings to give the Desktop a static IP to see if that would help. But back in Room A, the Desktop still doesn't connect. Based off of other internet searches, I also tried various combos of cmd commands like renew, release, flushdns, etc. to no avail.

If it was just a bad ethernet cable running through the house to room A, I would probably just accept it and move on, but the Laptop can connect fine there! At this point, the only thing I can conclude is:

1) Something about the ethernet connection wired to Room A is different from Room B.
2) Something is different about the Laptop that allows it to connect in both rooms.

If anyone has any ideas about what make 1) and 2) true and how I can make all devices work in Room A, I would really appreciate it.

 

[namtraab]

Nevermind, I figured out the solution:

I opened up the wall plate to inspect the ethernet cable. At the RJ45 jack I noticed that one cable, the white/green one, was not pushed all the way to the bottom, but kind of half way. So I pushed it down all the way, and voila there is an internet connection to the Desktop!

Kind of weird considering that the Laptop could still connect.

 

[GokAy]

The board is called a hub or switch.

Are the Ethernet ports of both desktop and laptop Gigabit speed? What does it say for Speed in Local Area Connection Status?

If you give static IP to desktop can it ping router or another desktop/laptop?