Dear george1421 ,
Finally i solved my problem. For Future guys ,
you need to add this line also to your /etc/dhcp/dhcpd.conf file .
next-server and some ip address , like : next-server 192.168.x.x.
my mistake was that i was writing it with “option” word . But next-server is string and it must be without option word. 🙂
Thank you for your support ,
This can be marked as solved .
Good Luck to all.