Insert DHCPD clients in local DNS

Hello Susers, I have a local server running a DHCP deamon and a local DNS (bind 8). I want that when DHCPD gives an IP for a client, it inserts this IP address into the local DNS. So you can clients by their names no matter what IP they were allocated. I used "ddns-update-style ad-hoc" in the /etc/dhcpd.conf and does not work.