[nsp] 192.168.x.y from upstream

[sthaug at nethelp.no]

> But do NOT ever filter this on your core network or you will break things that 
> the RFC1918 sourced packets may be carrying - most significantly pMTU conveyed 
> with ICMP. 

We have been running with RFC 1918 addresses filtered at all our
peering points for several years now, and we certainly intend to
continue this practice. Never had any negative feedback from our
customers due to this. YMMV.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no