When wall wiring acts like a good cross over and a bad straight

By techrepublic.20.chsg ·
I just ran about 30 ft. of CAT5e from one room in my house to another since I've moved two of our three computers to make room for a new baby.

Each end of the long wire is terminated by a rj45 port. I've re-checked and rewired it several times to make sure that each port is wired exactly the same (i.e. same color wire is hooked to position #1 on each port, etc.)

However, this does not work as expected. I'm getting anywhere from 20-100% packet loss when connecting a computer in room 2 with the router in room 1 (computer->patch cable->wall wiring->patch cable->router). However, when I connect a computer in room 2 to one in room 1 (computer->patch cable->wall wiring->patch cable->computer), the connection is great.

I have checked the patch cables to make sure that none are crossovers (which doesn't make sense since I've used them all previously to connect the computers directly to the router).

Any ideas?


This conversation is currently closed to new comments.

Thread display: Collapse - | Expand +

All Answers

Collapse -

Just one

by OH Smeg Moderator In reply to When wall wiring acts lik ...

Are you sure that both RJ45 Sockets are from the same maker?

Quite often different makers have different ways of wiring their sockets or at least the connectors on the back do not go to the same pin of the socket. You really need a Cable Tester to check the lead.

You can pickup a $20.00 one on E Bay and use this to correctly setup the wiring of the cable.


Collapse -

Two standards

by ozi Eagle In reply to Just one


Further to what Col said, above, there are two standards for Cat5 wiring, T568a and T568b. For a straight through connection both ends need to be to the same standard ( it doesn't matter which one as long as both ends are the same). As it happens if you mix the end standards you do get a crossover cable. Follow up on Col's suggestion of getting two sockets from the same maker, so that their color coding is to the same standard.


Collapse -

Yes, both the same

by techrepublic.20.chsg In reply to Two standards

Both are from the same manufacturer.

However, as the quality of the sockets is somewhat questionable, I might replace them if no other solution presents itself.

Collapse -

What about interference

by mjd420nova In reply to When wall wiring acts lik ...

Iy is possible that you've gotten the cable a little too close to some power wiring in the wall. This can cause all sorts of problems especially when neither end is grounded.

Collapse -

possible, yes...

by techrepublic.20.chsg In reply to What about interference

There is one point in the wiring that brings the cable in very close proximity with two power wires, so interference does make sense.

However, if the problem was interference, why am I getting perfect communication computer-to-computer?

Collapse -

cover it up

by kiran.maan In reply to When wall wiring acts lik ...

Try cover it in flexi pipe to avoid any power wire disturbance.

Is that packet is lost all time or specific ?

Collapse -

Have you tried using a Crossover cable as a Patch Lead

by OH Smeg Moderator In reply to When wall wiring acts lik ...

To see if you get communication?

It really sounds as if the Cable isn't correctly wired to the sockets.

I also keep any CAT Cable at least 12 inches away fro Electrical Wiring and more if it is the High Voltage type Wiring for 3 Phase Power Points and so on. In the US Finances or House heaters tend to draw a lot of power and you need to keep the CAT Cable further away from this.


Collapse -

Are you using the right color code / pair matching.

by 1bn0 In reply to When wall wiring acts lik ...

You state "(i.e. same color wire is hooked to position #1 on each port, etc.)"

The pairs must be matched for proper transmission
Pins 1&2
Pins 3&6
Pins 5&4 (they reverse for this pair)
Pins 7&8

each pair should be a matched wire set.


Yes it matters.

Collapse -

Correct termination

by ozi Eagle In reply to Are you using the right c ...


Note that the pairs do not terminate on adjacent pins. The n-tron reference about gives the correct pin connections.

With the cable entry end facing towards you and the locating tab down with pin 1 at the left, these are the pin connections .

Pin Color
T568A standard

1 Green/White
2 Green
3 Orange/White
4 Blue
5 Blue/White
6 Orange
7 Brown/White
8 Brown

T568B standard

Pin Color
T568A standard

1 Orange/White
2 Orange
3 Green/White
4 Blue
5 Blue/White
6 Green
7 Brown/White
8 Brown

NOTE, only the Green and Orange pairs are actually used, the Brown and Blue do nothing.

Sometimes it is possible to utilise these two unused pairs to connect a second computer, however, be aware that crossover may occur and therefore only use one computer at a time.


Edited to remove duplication

Collapse -

the resolution

Before I say what the real problem ended up being, let me say that I did double and triple check the wiring initially. verify that the cable was good and the being run right next to some electric cables wasn't causing issues (it wasn't) I tore off the ports and put plugs on each end. The cable worked great.

Then I rewired the ports (again). Lo and behold, it works fine now. My guess is that originally I mistook the white/brown wire for the white/orange wire or something like that.

Thanks everyone for their help!

Related Discussions

Related Forums