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Author Topic: UTP cable pin-outs confusion  (Read 975 times)

Shades

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UTP cable pin-outs confusion
« on: March 03, 2019, 11:03 AM »
Let me begin with two statements:
1 - There is no general hardware section in the DC forum, so I chose the next best general section.
2 - I make my own UTP cables, for almost 15 years already.

Google wasn't that helpful regarding my question. Most of the (CAT5e) cables I prepared in the beginning are still in use today. I know about TIA568A and B cable pin-out standards. My preference is B.

However, lately I see cables on different locations appear that use a different pin-out. All the pairs are next to each other, instead of switching cables from different pairs as the 568 standards suggest. These are definitely not cross-cables or straight cables either. I know about the differences between the CAT5e/CAT6/CAT7 cable categories, but I am not aware that this had implications on the cable pin-out.

Other forums tell me that this isn't the case, sites like this one tell me that this isn't the case, so now I am getting confused. There is not much necessary to accomplish that, I know. But still, can anyone here enlighten me about the subject or point me to documentation?


Ath

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Re: UTP cable pin-outs confusion
« Reply #1 on: March 03, 2019, 01:05 PM »
Hm, intriquing question. Like you I've mostly made utp cables (and coax before that) myself. I'd declare it nearly impossible for the pinout to change from cat5 to cat6 to cat7, as the cables are backward compatible. And I've not found any evidence for changes in pinout, so far.

Having said that, I have a few possible causes for your 'color confusion':
  • The cables are possibly made by unexperienced/uninterested people, and they just 'made it work' by creating a 1:1 connection, regardless of wire pairs (simple wiretest equipment can't detect pairing, only correct connections)
  • The wires have a non-color-related pairing (highly unlikely though), you'd have to cut open a cable to verify

When aiming for cat6/cat7 speeds, I'd verify that the cables are pair-connected as required (and ideally shielded as well) to avoid hard to debug networking issues. The shielding requirements for cat6/cat7 make it quite hard to make these yourself, unless you have access to the professional tools for crimping that type of cable.

4wd

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Re: UTP cable pin-outs confusion
« Reply #2 on: March 03, 2019, 05:27 PM »
All the pairs are next to each other, instead of switching cables from different pairs as the 568 standards suggest.

If Wikipediaw can be believed it's not necessary for 1000Base-T or higher to follow 568A/B, (just finished wiring up IP cameras to 568B ... before I found that B is deprecated in favour of A and is preferred in Australia :-\ ... oh well, not critical for IP cams), because of the advent of Auto-MDI(X) and attendant technologies.

Gigabit and faster Ethernet links over twisted pair cable use all four cable pairs for simultaneous transmission in both directions. For this reason, there are no dedicated transmit and receive pairs, and consequently, crossover cables are never required for 1000BASE-T communication. The physical medium attachment sublayer (PMA) provides identification of each pair and usually continues to work even over cables where the pairs are unusually swapped or crossed.

I'd go with Ath's first option since it's a lot easier to terminate cables where the pairs are side-by-side than split a pair over the connector, (as the standard does), especially if you're using solid core wiring.

It'd be interesting to see if they worked when dropped into a 100Base-T environment, with or without Auto-MDI(X).
« Last Edit: March 03, 2019, 05:36 PM by 4wd »