> This is a favorite interview type question of mine, but I won't
> disqualify a candidate if they can't come up with the reason. It's more
> of a probe for historical domain knowledge (one of many I'll slip in).

It's an interesting flag at interview for me, if it comes up, but I wouldn't normally talk about it unless the candidate does first.

 

-If they don't know or mention classful networking at all, they're new (relatively, I'm old), and that's fine.

 

-If they can get it right, they're either a long-timer or have done some network history.

 

-If they try to use it, and get it wrong, or can't properly explain it, there's a warning that they've been cramming network skills from some old and/or low-quality sources.  I'd start probing for other warning signs like /24s on point-to-point serial links, RIPv1, and the like.

 

Regards,

Tim.