[c-nsp] Redundant switch fabric

[Buhrmaster, Gary]

> I have a solution design that requires redundant switch 
> fabrics. I am interpreting this beyond just have redundant 
> supervisors meaning redundant backplanes on the switch cards. 
> Do the 6500 and 4500 support redundant fabrics? Will a 6748 
> function with one trace failed?

If you really need redundancy at those levels, you
really want two chassis.  While rare, even the
chassis can fail (as documented, about once a year,
by someone on this list), and for "interesting"
problems TAC may want you to OIR cards that cause
"interesting" results on the entire chassis,
and no matter how good the hardware, software bugs
can always take out the entire box.

In box reliability is valuable and desirable, but
when you need really high availability, you have
to at least consider an out of the box solution.