According to Alan Barrett:
> 
> Or mark individual IP addresses `strong' or `weak'; see below for
> justification.
> 
> [ explanation omitted ]

I find Alan's suggestion very seductive.  In particular, Ted Lemon has 
often complained that it is impossible to determine on which interface 
a packet has "originated", which Alan's suggestion of keeping around 
the associated interface ID for each "strong" IP number may assist in 
determining.

++L