IP Address allocation/asigment tools

[Ramarajan, Arvind, ALABS]

Hi,
 Would like to know about any off the shelf or freeware software
application/tools out there to manage IP address (allocate/assign both
for IPv4 and IPv6) in a SP network environment. Pros and Cons are
welcome.
                                                        Thanx -->
                                                                Arvind.