can some body help me to do the configurations.........

as a default rule , block every MAC adrresses and

let few of known MACs to Allow come in to a DHCP server  using iptables ................pls

i did some configurations , but those r not working .

if all the input , forward , output DROP in the default policies , no one can access the dhco server ....is it ?
but my dhcp clients tkaing the ips.....how come this ?

pls reply me asap

thanx