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Re: Problems connectivity GE on Foundry BigIron to Cisco 2950T
- From: Mark Smith
- Date: Sun Jan 15 19:41:22 2006
On Mon, 16 Jan 2006 00:24:35 +0000 (GMT Standard Time)
Sam Stickland <firstname.lastname@example.org> wrote:
> On Mon, 16 Jan 2006, Mark Smith wrote:
> > On Sun, 15 Jan 2006 23:50:07 +0000 (GMT Standard Time)
> > Sam Stickland <email@example.com> 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
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.
"Sheep are slow and tasty, and therefore must remain constantly
- Bruce Schneier, "Beyond Fear"