PC connecting on the middle of ethernet cable

Question

I have a 4-5 meter long UTP cable from my router to a wall socket (socket A) which works fine.

Original setup:

          4-5 meter cable            
Router ------------------- Socket A 

The original setup worked fine.

I wanted to extend this cable to another wall socket so I used a 4 meter long cable. I connected its pin to the existing socket (A) whithout removing the existing connections and mounted the other end of the cable to socket B. I did a straigth through wiring from A to B, checked with a multimeter and measured 0 ohm betwen end of wires although for some wires I measured a 4-5 ohm (don't know why). I did measuring right from the socket pins.

New setup:

        4-5 meter cable                  Added second cable
Router ------------------- Socket A -------------------------- Socket B

                           Now fails                           Works

My problem is that if I connect a PC to socket B then the network works fine. If I connect the PC to socket A the network icon in Windows even doesn't display that a valid connection is present.

Is there any restriction that I cannot fork from the middle of an existing cabling to connect my network device? Or simply I did some mistake in mounting the wires to the socket A, that's why my network connection does not work from socket A ?

Of course I don't plan to use two network devices simoultaneousely on socket A and B but thought that can use or on socket A or on B.

Answer 1

No, you can't (reliably) do what you've done. First off, there is no standard punchdown block (or otherwise), so I am guessing you are using a screw terminal block? That is not rated for CAT5(e), twists are not maintained. You might be able to get away with it for awhile though, but I wouldn't bother.

It's my understanding that by having a lengthy unterminated wire hanging off your network you will introduce problems where the signal will bounce off the end, potentially causing destructive interference, much like the thinnet coax days.

Buy some punch down jacks and a 1ft jumper and simply unplug the end not in use, or better yet pick up a cheap switch. (It's probably just as cheap as the punch down jacks these days...)

Answer 2

Ethernet wiring is not like analog telephone wiring. Unlike telephone wiring, you can't daisy chain from the back of one Ethernet wall jack to another Ethernet wall jack, even if you don't plan on using both wall jacks at the same time. That kind of splice doesn't simply doesn't guarantee the signal integrity required by 1000BASE-T (gigabit Ethernet).

If you get the twisted pairs right and your distance isn't that long, you might get lucky and it might just happen to work, but you're not following the standard/specification (the rules that are designed to guarantee success).