[87957] in North American Network Operators' Group
Re: Problems connectivity GE on Foundry BigIron to Cisco 2950T
daemon@ATHENA.MIT.EDU (Sam Stickland)
Sun Jan 15 19:51:17 2006
Date: Mon, 16 Jan 2006 00:50:33 +0000 (GMT Standard Time)
From: Sam Stickland <sam_ml@spacething.org>
To: nanog@nanog.org
Cc: Mark Smith <random@72616e646f6d20323030342d30342d31360a.nosense.org>
In-Reply-To: <Pine.WNT.4.64.0601160018010.2524@p4-2800>
Errors-To: owner-nanog@merit.edu
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,
S
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:
>>
>>>
>>> Hi,
>>
>> <snip>
>>
>>>
>>> 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.
>
> Sam
>
