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Mixing cross over and straight through cables on a switch

Posted on 2007-04-04
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Last Modified: 2012-06-27
Dear experts,

My cable modem is connected to my computer using a cross over cable (well, at that's what it seems like to me - it says "X over" on the RJ45 connector). We wanted one more computer to be able to access the internet at the same time so we put an Edimax 8-port switch and plugged the cross over cable from the modem into one of the switch's ports. Then we bought two straight through cables and plugged both into the switch also.

It worked for about two weeks; we could surf simultaneously and play network games. Then one day the switch wouldn't turn on. Since the switch was still under warranty, we brought it to the vendor who confirmed that it was not working.

I don't know if I'm wrong, but could the damage have been done by mixing cross over and straight through cables into the switch?

Here's more info on the switch (I'm using the 8-port model):
http://www.edimax.com.tw/html/english/products/ES-31xxP.htm

Thanks!
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Question by:jericotolentino
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InteraX earned 80 total points
ID: 18849462
Hello jericotolentino,

Highly unlikely. As crossover cables are designed to enable host-to-host or switch-to-switch communication and this is used in most business environments, I would expect that if there was an issue in doing this, many people would be reporting issues.

Regards,

InteraX
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by:Bobby_Thekkekandam
ID: 18849795
Agreed with InteraX.

All a Crossover Cable does is reverse the Rx and Tx wires on one end within the Cat5 cable. One end will follow the T568A pin/pair assignment, and the other end will follow the T568B orientation.

<img src="http://duxcw.com/faq/network/uplink.gif">

The left figure is a straight through, and the right figure is the the pin/pair mapping of the crossover. Even if you incorrectly use a crossover to connect, say, a switch and a PC, the voltage is too low to cause any problems. In fact many newer switches have a feature called Auto-MDIX, which allows the interface to detect which orientation the Tx and Rx are and reverse if appropriate. This means that if you connected another switch or a PC to the same port, it would not matter whether you used a straight-through or crossover cable. The switch will adjust its own Rx and Tx accordingly.

So, rest assured that using a mix of crossover and straight-through cabling did not damage your switch. Without performing a Failure Analysis test on the switch in a lab environment, it will probably be impossible to know why it failed. It may simply be a manufacturing defect, improper handling during packaging (causing ESD), power surge, or myriad other causes.

Hope that helps,

Bobby
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by:jericotolentino
ID: 18850292
Wow, that's a relief. I thought I had damaged it. Anyway, this is just for home use, so the worst thing that could happen is that we won't be able to go online simultaneously. Thanks to everyone who contributed!
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by:InteraX
ID: 18850521
Thanks for the points.
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