Problem: Trouble with ethernet connection in some rooms and some computers (but not all rooms or all computers)

[breanainneire]

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?

I have done "ipconfig /all" for both the Desktop and the Laptop in both rooms and the results are posted below. I realize from the results from Desktop in Room A 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 and connected, I 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.

<IP information removed by moderator. Please refrain from posting this information in the future. - G>

 

[Ralston18]

Brean,

The "board" you referred to is a patch panel.

(Patch cables: used between patch panel ports and routers, wall outlets and network devices, etc.. As opposed to the cable plant which is the permanent wiring run from the patch panel to the various room wall outlets. Hopefully someone labeled or otherwise provided documentation such as a diagram to show which patch panel ports serve/go to which rooms.)

What ethernet patch cables are you using: i.e., Cat 3, Cat 5....?

Does not take too much of a difference to allow a patch cable to work in one situation and not in another.

Can you repeat your test results with an entirely different set of "moveable" ethernet cables; i.e., the ethernet patch cables?

 

[breanainneire]

I have actually fixed the problem at last: I opened up the wall plate in Room A and inspected the connection of the wall ethernet cable and noticed that one wire (the white/green one) was kind of half way down the slot. So I pushed it all the way down like the others. And, then the Desktop connected to the internet at last! Kind of strange that the Laptop was still able to connect despite that wire being misplaced a bit (and yes, I am sure it wasn't just connecting through wifi).

 

[Ralston18]

Excellent!

Wall plate and patch panel inspections would have been the next step.

Desktop was probably just more "sensitive" (for lack of a better word) than the laptop to the poor connection you found.

The same sort of thing can occur in patch cables as well. Just easier to try swapping patch cables first as opposed to opening up wall plates that can be behind desks, couches, etc. and include other circuits for telephone, cable TV, audio systems, and so forth. I try to work from simplest to more complex.

Some rainy day you may wish to check all of the patch panel and ethernet connections (slots) in the same manner. Punchdown connections do tend to wiggle and move and therefore loosen over time. Especially if the wire gauge is marginal for the connecting pins.