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Re: Problems connectivity GE on Foundry BigIron to Cisco 2950T
From: Sam Stickland <sam_ml () spacething org>
Date: Mon, 16 Jan 2006 00:50:33 +0000 (GMT Standard Time)

Wikipedia reveals all. http://en.wikipedia.org/wiki/Crossover_cable

Turns out that for 1000Base-T crossovers pairs 2 and 3, and 1 and 4 have to swapped. Standard TIA-568B to TIA-568A over swaps 2 and 3.

Auto MDI/MDI-X is optional in the 1000Base-T spec so the way forward is to try a straight cable and if that fails I'll have to make up a 1000Base-T crossover cable.

Thanks for all the help people,


On Mon, 16 Jan 2006, Sam Stickland wrote:

On Mon, 16 Jan 2006, Mark Smith wrote:

On Sun, 15 Jan 2006 23:50:07 +0000 (GMT Standard Time)
Sam Stickland <sam_ml () spacething org> wrote:



The cabling arrangement is:

Foundry -- Straight -- Patch -- Underfloor -- Patch -- Crossover -- Cisco
  GBIC       Cable      Panel     Straight     Panel      Cable

If I replace the final crossover cable with a straight,
Just do that ^^^ and give it a try.

Will do.

If that fails I might have to dig out a non-passive 1000SX to 1000-BaseT media convertor that's on one of the other sites and give that a try.

Btw, several people have suggested "speed nonegotiate" on the cisco speed. This command is only supported on GBIC slots on cisco, not on fixed 1000Base-T interfaces (at least not a Sup720/WS-X6748-GE-TX).

I also found this reference about the clock signals in use on 1000Base-T:

"Synchronous transmission
1000BASE-T is based on synchronous transmission to facilitate the cancelation of Echo/NEXT/FEXT interferences at the receivers. To achieve synchronous transmission between the two PHYs at the ends of a link, a master-slave clocking relationship is established by the PHYs. The master-slave relationship between two stations sharing a link segment is established during auto-negotiation. The master PHY uses an external clock to determine the timing of transmitter and receiver operations. This master clock is also provided to the other stations in the network. The slave PHY recovers the clock from the received signal and uses it to determine the timing of transmitter operations. In a typical network, the PHY at the repeater will become the master and the PHY at the data terminal equipment (DTE) will become the slave."

So it would appear that auto-negotiation is a requirement in 1000Base-T.


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