Allowing DHCP for a particular client

Allowing only a particular dhcp client :
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#  /sbin/modprobe ipt_mac
                
#iptables -A INPUT -p UDP --dport 67 --sport 68 -m mac --mac-source xx:xx:xx:xx:xx:xx -j ACCEPT



DHCP server runs on UDP port 67
DHCP client runs on UDP port 68

Here mac-source is dhcp client mac address.