Re: Problems connectivity GE on Foundry BigIron to Cisco 2950T

[Sam Stickland <sam_ml () spacething org>]

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"