Say I am operating a public service. Generally, people behave, but every once in a while someone does not, and it is usually good to know who you're receiving that blessing from.
- that it's a good idea to keep track of recent IPs your users use,
- that service providers generally give their customers a /64 block, and
- software such as radvd or even isc-dhcp-server assume they get nothing less than a /64 block
- that due to privacy extensions, at least Windows allocates multiple addresses in the /64 block that it rotates between (allocating more as it goes on)
would it be a good idea to just throw away the final 64 bit of an IPv6 address, and just keep track of the first 64 bit?