[c-nsp] SFP & GBIC module compatibility

[Will Hargrave]

Phil Mayers wrote:

>  * Had duplicate serial numbers - in one case, two SX and an LX SFP had 
> the same serial number in the EEPROM. In no case was the serial on the 
> label matched by the serial in the EEPROM.

Note that this, at least on 6509, causes the box to err-disable the port
with the duplicate IDPROM serial... ugh!!! Not what you want in a maint
window in the middle of the night.

Those optics which Phil describes are a bunch of old crap; I'm sure
better quality products dropped into my gravy upon pulling a Christmas
cracker a few days ago ;-)