How to clear DHCP leases in OS X Server (v4.1.3-14S1127) on Yosemite 10.10.4
Solution 1:
I found this but can not test since I do not have your set up.
Stop the dhcp server either through Server Admin or from a command line command of
sudo serveradmin stop dhcp.delete the file /var/db/dhcpd_leases. You will need root access. Terminal command of
sudo rm -f /var/db/dhcpd_leasesRestart dhcp via server admin or by terminal command of
sudo serveradmin start dhcp
Be very careful when deleting files in terminal!