iptables: MAC binding for subnet

Hello,
I have a gateway and would like to allow only a few systems identified through MAC for a subnet. I have tried but failed with iptables and the error message is non-informative. It appears to me that I need to use PREROUTING but unable to actually use it as iptables is not accepting. Can anyone share the method please?
TIA,
-Dviip

Use THIS as a guide. You will have to substitute INPUT for what every you are trying to do.