I am not an engineer but I’m having problems with my small network in my business. I have 11 computers after 13 yrs am having major problems. My network keeps shutting down, and my dental software on my server keeps crashing. My question is that I think my original installer of my low voltage used Type A to connect to the patch panel since the orange and green sets of wires are flipped. Does this matter. The patch cords I buy are over the counter at frys and I assume those are B type. Would this be affecting my network slowdown and crashing? It was ok for the first 10 yrs every once and a while shutting down, but now that we have added more computer thruout the years, it freezes at least 3x a day. I have a network gigibit adapter. Thanks in advance.

  • You can hire, for a couple of hours, a certified installer with a tester (the very expensive kind of tester, in the price neighborhood of some of your dental equipment) to test and correct any cable problems. Freezing can also be a symptom of computer or application trouble, too.
    – Ron Maupin
    Dec 10, 2017 at 17:30

2 Answers 2


Short answer: A-type or B-type cables don't matter as long as both sides of a cable are the same

Long answer: Although there are T568A and T568B terminated cables, both types can be used interchangeably. The difference is in color code only - the important detail is that the pairs match which can be taken for granted with retail cables.

The only actual difference is when one end of a cable is terminated in T568A order and the other in T568B order - this is a crossover cable that used to be necessary for switch-to-switch or computer-to-computer connections with early 10 and 100 Mbit/s equipment up to ca. 1999. Later devices usually support Auto MDI-X which makes crossover cables unnecessary.

For the problem at hand and assuming the trouble started once gigabit speeds where used, you can try the following:

  1. check error counters on network interfaces and on the switch, look for collisions, FCS error, runts, jabbers
  2. have your structured cabling checked; with gigabit speed, flawed termination or damaged cables can cause problems even when the cables worked fine with 100 Mbit/s
  3. configure problematic links down to 100 Mbit/s - try (in preferred order)
    1. auto-100 on the switch (leaves autonegotiation active)
    2. 100 MBit/s full-duplex on both sides (only when this is possible on both the switch and the computer's network interface)
    3. 100 Mbit/s half-duplex (only with a non-managed switch)

Agreed with Zac67. If you connect a cable that has T568A on both ends with a cable that has T568B at both ends, the result is that its still a straight through cable. In other words, pins 1-8 will be pins 1-8 at the other end, in the respective order. After you have checked all the cabling Zac67 have suggested, the next step is to go over server maintenance tasks -- check for old hardware that's breaking. And then if you know your hardware is fine, ask your software vendor if your practice (number of dental photos, etc) outgrown the software.

  • Good point - I actually lost focus after pointing out the potential cable issues.
    – Zac67
    Jan 9, 2018 at 19:07

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