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Re: Problems connectivity GE on Foundry BigIron to Cisco 2950T
From: Mark Smith <random () 72616e646f6d20323030342d30342d31360a nosense org>
Date: Mon, 16 Jan 2006 11:10:11 +1030


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"


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