Как привязать user's IP address к MAC ?

Не знаю что такое freesco, но по поводу Linux - man iptables
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--mac-source

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mac
--mac-source [!] address
Match source MAC address. It must be of the form XX:XX:XX:XX:XX:XX. Note that this only makes sense for packets entering the PREROUTING, FORWARD or INPUT chains for packets coming from an ethernet device.