Unpaired pairs on RJ45 cables
hebus888 Posted messages 851 Registration date Status Membre Last intervention -
Hello,
An electrician wired a network in my house like this (5 years ago):
The fiber arrival is redirected to a router (10/100/1000) that "distributes" internet to several RJ45 sockets in the house (the cables are all cat 6).
A few days ago, I wanted to check the continuity of the cables in order to identify the sockets on the router, but it turns out that the pairs are not respected at all.
For example, port 1 on one end is connected to port 7 on the other end and port 3 is connected to port 6 (but there are some correct ones, anyway), etc... and it's different for all the cables!!!
My question is as follows:
What is the impact on the quality of my connection?
Thanks in advance.
3 réponses
Hi,
When you talk about ports, I think you mean the positions on the RJ45?
If you connect 1 to 7, the cable simply won't work, whereas swapping 3 and 6 and vice versa shouldn't have any impact, the pair is still respected.
You can swap the order of the wires in a twisted pair, it doesn't change the operation.
What you should not do is unpair and even less connect a different point at each end with the same wire.
And there you go, here it is ....
But goodness, the spacing is so annoying!!
I am indeed talking about the colored wires that are not wired “normally.”
If we assume that the straight RJ45 cable is like in the photo, then mine look more like crossed cables but in a messy way!!!
For example, the brown wire in 8 is in 6 on the other side. This can't work ....
It could be that this is a crossed cable (double cross)
simple cross:
1 - 3
2 - 6
3 - 1
4 - 4
5 - 5
6 - 2
7 - 7
8 - 8
double cross:
1 - 3
2 - 6
3 - 1
4 - 7
5 - 8
6 - 2
7 - 4
8 - 5
Simple crossed cables were for 10/100 and doubles for some old gigabit switches.
But now gigabit ports are auto MDI/MDIX and automatically crossover or direct.
However, we never wire wall jacks as crossed, always straight.
I advise you to put everything back in place and run the tester again to check.
The examples of inversions I give may not be the real ones because I admit I don't remember the actual inversions (which I hadn't noted down anyway!)
Regarding what you say about auto MDI/MDIX switches, doesn't that mean that regardless of how the pairs are connected (whether done correctly or haphazardly), the switch "corrects" the error???
How can we tell if it is auto MDI/MDIX?
