Problems connectivity GE on Foundry BigIron to Cisco 2950T

Mon Jan 16 00:40:11 UTC 2006

On Mon, 16 Jan 2006 00:24:35 +0000 (GMT Standard Time)
Sam Stickland <sam_ml at 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 at 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"