topic Re: reversed wiring on the RJ45 in Wireless

reversed wiring on the RJ45

skiingbandit — Sun, 04 Jul 2021 03:14:35 GMT

I am a installer and I reversed the wiring on the RJ45 connecter that plugs into the ethernet port on a Aironet wireless access point! It was already connected to the switch.

So Pin 1 on the WAP RJ45 connector is Pin 8 at the switch and so on.

The status light flashed green for about 30 seconds then went steady green. IS THIS OK?? Will it still work?? We just install the units and dont do the programming or testing. And I wont be able to go back and change the wiring unless I tell someone.

Please does anyone know the answer to this? I will have to eat crow if I have to go back and redo the connector.

Mark

614-876-6321

Thx

Re: reversed wiring on the RJ45

mages_mark — Thu, 26 May 2011 17:33:45 GMT

You should do the job they paid you to do correctly.

Even if this switch is capable of autosensing, that doesn't mean that the next device they try to plug in will work.

If you're a professional installer, you should have a Fluke, and use it before you call the job complete.

Re: reversed wiring on the RJ45

skiingbandit — Fri, 27 May 2011 16:38:32 GMT

I went and fixed it the next day. But still curious to know if it would work both ways. So some switches are capable of "autosensing" ? The wiring can be totally wrong and it will still work?

Re: reversed wiring on the RJ45

Nicolas Darchis — Fri, 27 May 2011 17:48:32 GMT

I'm not so much into cables. However, autosensing on the switch refers to the ability to detect if a straight or a crossover cable was plugged.

The crossover cable is crossing specific pair, it's not a reverse of all connections. So I'd be surprised that any device would have made sense out of that.

Re: reversed wiring on the RJ45

skiingbandit — Fri, 27 May 2011 19:09:47 GMT

I have looked through the data sheets on both the switch a Cisco 3750 and the AP a Cisco 3502 and I cant find any reference to the pin out on the ethernet port- BUT it still worked both ways!! Since it is POE the power is being provided on 1 pair so if the wiring is reversed - the AP should not have even powered up if the wiring was reversed - but it did. It goes through the boot cycle flashing green - then goes steady green! That means the ethernet is OK?

Now when I say it worked - I mean only that the AP powered up and got a link light. So how can this be?

The problem is fixed but the mystery remains

Re: reversed wiring on the RJ45

Leo Laohoo — Sat, 28 May 2011 04:24:17 GMT

What 3750 model exactly? Is it a plain 3750 or a 3750G or 3750X or 3750E?

The reason why I'm asking is because the 3750G, X and E support copper TDR. Sadly, the plain 3750 doesn't. *Mumble*, *mumble*, *mumble* ...

We've just finish rolling out >1000 APs and all I can say that I'm grateful someone enabled TDR support on the 2960 because we rejected alot of cable works from reputable companies. The common fault we found were: not all four pairs were terminated and Cat5E cables were JOINED with Cat6 cables.

This is coupled with faulty patch cables from another reputable manufacturer.