[ Thanks to artemn for this link. ]
If you are sysadmin at organization that holds pool of
IP addresses and allocates its parts to clients then you must use
IP address management tools to track used, reserved, allocated or
free IP addresses. It usually prevents an overhead and allows to
have clear picture of IP addresses resources usage within an
organization on the whole. For example, it may be useful to know
how many free IP networks are available for clients and take
necessary actions before it happens there’s nothing to allocate.IP address management tools may also make it possible for you as
a sysadmin to prevent fragmentation of IP addresses usage.
Generally if you work at LIR then IP address management tool is a
must.