Please help: ptp links addresses

>1- using a /30 subnet for each link:
>   in this way both ends of the link have a unique address (binary
>   01 and 10), but two addresses (binary 00 and 11) cannot be used,
>   so 50% of the address space used is wasted. This should be
>   avoided if possible because the address space required is
>   really large.

The usage is actually 75%, as there are effectively three addresses:
the two ends (00 and 01) and the broadcast address for the network
(11).  10 is the unused address.

Mike