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TOPIC: UTP cable standards

UTP cable standards 8 years 4 months ago #26836

  • Starfire
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Hi firewall cx. Been a while since I was on these forums but I am getting back into networking so I am dusting off the knowledge. (quite surprising what I have retained after 18 months out)

I've been going through utp cabling standards t-568A and t-568b shown here http://www.firewall.cx/cabling_straight.php and I have a little question that's confusing me.

In t-568b, pins 1&2 are used to transmit but in t-568a, these pins are used to recieve. This implies that the network devices themselves must have their ports set to listen at one of these specific standards.

Could anyone shed any light on this ?

Thanks
Star.
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Re: UTP cable standards 8 years 4 months ago #26841

  • S0lo
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In t-568b, pins 1&2 are used to transmit but in t-568a, these pins are used to recieve. This implies that the network devices themselves must have their ports set to listen at one of these specific standards.

Hello Starfire :)

Yes your right. furthermore, PCs and Routers have the same port types, (PINs 1,2 as TX and PINs 3,6 as RX). Switches and Hubs have the crossed types (PINs 1,2 as RX and PINs 3,6 as TX)

The rule is: TX should be always connected to RX. TX to TX will not work. RX to RX will not work. Think of the all this and you will come up with the following rules:

Connecting a PC to Router: Need cross over cable
Connecting a Switch to Hub: Need cross over cable
Connecting same devices: Need cross over cable
Anything else: Need a straight through cable

The exception is that some new PCs (and may be other devices) have the ability to auto detect the other side port and automatically flip their pins accordingly. In this case any cable will work.
Studying CCNP...

Ammar Muqaddas
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Re: UTP cable standards 8 years 4 months ago #26850

  • Starfire
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Terrific,

Thanks Solo
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Re: UTP cable standards 8 years 4 months ago #26859

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Glad to help :)
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Ammar Muqaddas
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