568A (ISDN) and 568B (AT&T) UTP wiring standards

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Does anybody know of standards, guidelines or recommendations that govern pairs 1 and 4 in a UTP crossover cable? These are the two pairs than DO NOT play a part in the transmission of data in the TIA/EIA standard. The TIA standard says leave them as they are. I teach a hands-on networking course with real hardware, and have found that some manufacturers either swap pairs 1 and 4 in a crossover assembly, or leave the pairs in their TIA defined position and swap the individual wires in each of these pairs. I can find no way to explain these variations to my students. If anyone can help you'll be demystifying part of our industry to me as well as the students.....Thank you
ASKED: May 31, 2006  7:10 AM
UPDATED: May 31, 2006  10:01 AM

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According to my memory, you just leave straight on pair 1 (ping 4,5) and pair 4 (ping 7,8) on crossover cable for fast ethernet/ethernet uses. You have to do all 4 pairs crossover for gigabit ethernet application.
Some new gigabit switchports for Cisco will detect automatically and crossover internally so you never need cross over cable on those ports.
I don’t know where to find the standard documents. Here is just a link to the SearchNetworking definition.

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  • Onamission
    Try this http://www.duxcw.com/digest/Howto/network/cable/cable5.htm Pair 1 = Wire 1 and 2 Pair 2 = Wire 3 and 6 Reversr these "pairs" for a crossover cable
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  • Jemcginness
    See, for example, http://www.finnie.org/text/network-tips/ Gigabit Ethernet uses all 4 pairs and a crossover cable built in the "old" standard way will often not work. The blue and brown pairs have to be crossed over as well. (Ryan's diagram violates the rule of "stripe on odds, solids on evens", so I'm not sure if it is strictly correct but, with differential signaling, it may "just work".)
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