[nsp] using /31s

[Roger]

Mike Sawicki wrote:

>Jeff is right.  The only time I ever use /31's is to reference ip pairs 
>in filtering/acl applications.  This is really the only realm in
>which they are valid.  Try 'ip unnumbered' if you are getting
>desperate for space.
>  
>
The problem w/

'ip unnumbered'

Is that you now depend on another interface being up.  Granted the other 
interface is usually a ethernet interface which is pretty reliable, you 
open yourself up to one more point of failure.