How is this possible??

[pds]

I just had to re-route an ethernet cable in the office and it required me to cut off the rj45 and replace it after rethreading the cable through the new route.

I cut off the end so I'd remake the cable the same way - looking at the bottom of the rj left to right - wo-o-wg-b-wb-g-wbr-br.
When I remade the end I built it backwards, switch the striped an the solid. i.e. o-wo-b-wg-g-wb-br-wbr.

Now that's possible because, brain fart. But the real Q is how come when I plugged it in - it worked!!!
The next day I was fiddling with the end I had cut off and got to thinking this is not how I made the new end. I pulled it out this am and - backwards.

So I made a new end the right way and plugged it in and - Violah! of course it worked. But - why did they both work?

 

[SGilbert]

Beats me!
Why do USB-C & Lightning plugs work downside up & upside down? Sure hope you don't stay up all night tonight pondering this stuff!

FWIW, I would have made a bigger hole for the plug.

 

[Satcomer]

The original installer made have made the same mistake seems the possible answer! Don't over think the situation just break a sigh of relief that your error made it work! As retired Network Tech I have seemed so-called experts make that very mistake from time to time and just made laugh!

 

[pds]

Not loosing sleep- for sure.
Bigger holes - my kinda solution.
But we had to pull it out of many through-the-wall spots to run it through the basement, so - OFF WITH ITS HEAD!!!

I had a high school computer club help me make cables in another life. Some of them had 6 wires right and the brown pair backwards and the cables wouldn't work. Back in the day I had a coax ethernet set up in a newsroom in Cairo. Sometimes leaving off a terminator made the network crash, but if you took off another one somewhere else it would solve conflict problems.

Ethernet==Vodoo!

 

[cyclyst1964]

I know it's been a while since you posted your question, but I've just started looking at this site again after being away for a good, long while.

What you had done when you wired one end directly opposite of the other is that you created what we call a crossover cable.
Traditionally a crossover cable is used to connect two computers directly to one another for diagnostics. They can also be used to connect a router directly to another router, two switches together, or a router to a switch.

Most likely the reason it worked anyway is that most modern enterprise network devices can determine the Ethernet connection types and select the correct wires for transmitting and receiving data using a technology called Auto-MDI/MDIX (Auto Medium Dependent Interface Crossover Technology).

When using your conventional straight through Ethernet cable, your Auto-MDI/MDIX enabled switch or router will use Auto-MDI/MDIX to turn it into a crossover cable whenever it is optimal.
If you accidentally use a crossover cable, the Auto-MDI/MDIX enabled device will select the correct pairs of wires to turn it back into a straight through cable to optimize data transmission.

Still, you did the right thing correcting the wiring of that cable.