For cPanel & WHM version 56
(Home >> IP Functions >> Rebuild the IP Address Pool)
This feature scans the server's bound IP addresses in order to locate IP addresses that are not linked to a domain.
Rebuild the IP address pool
If the system determines that there are available, unused IP addresses, it places those IP addresses back into the IP address pool. When you create new accounts, cPanel & WHM uses the addresses from this pool.
To rebuild the IP address pool, click Proceed. After the scan finishes, the interface displays the number of free IP addresses in your IP address pool.