not removed dns entry on a system exit from network

[Mohammad Ebrahim Abravi]

hi
using samba 4.0.17 and bind 9.8.0 and dhcp server

problem:
if user login from a machine in my network, automatically add ip and
machine name to zone file. if machine ip changed zone automatically update
but if machine is down or exit from network, name and ip stay in zone file
and if use 'host .... ' cammed show ip. if ip assign to another  machine,
machine not add to dns zone.