[87958] 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 19:53:27 2006
Date: Mon, 16 Jan 2006 00:51:47 +0000 (GMT Standard Time)
From: Sam Stickland <sam_ml@spacething.org>
To: Mark Smith <random@72616e646f6d20323030342d30342d31360a.nosense.org>
Cc: nanog@nanog.org
In-Reply-To: <20060116111011.2381a740.random@72616e646f6d20323030342d30342d31360a.nosense.org>
Errors-To: owner-nanog@merit.edu
Thanks Mark - just found the same thing out myself :)
S
On Mon, 16 Jan 2006, Mark Smith wrote:
>
> On Mon, 16 Jan 2006 00:24:35 +0000 (GMT Standard Time)
> Sam Stickland <sam_ml@spacething.org> 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.
>>
>
> Having done a bit more looking into this myself, one thing that might be
> a cause is the cross-over, in the sense that if it is a 100BASE-T
> crossover, only two of the pairs will be crossed, and the other two
> pairs are usually wired straight.
>
> A GigE cross over, assuming you need one if you're ports don't support
> automatic cross over, has all four pairs crossed over
> (1-3,2-6,3-1,6-2,4-7,5-8,7-4,8-5). My guess would be that if a device
> only detects two of the four pairs crossed, it drops back to 100BASE-T.
> In other words, GigE cross overs are backwards compatible with
> 10/100BASE-T, but 10/100BASE-T crossovers aren't forward compatible with
> GigE.
>
> A GigE rated straight through path would be the first thing I'd test,
> after that, possibly try a GigE crossover somewhere between the devices.
>
> Regards,
> Mark.
>
>
> --
>
> "Sheep are slow and tasty, and therefore must remain constantly
> alert."
> - Bruce Schneier, "Beyond Fear"
>
