drop by mac address, but only to packets to other interface

Jasbir Khehra jasbir.k at gmail.com
Wed Nov 8 08:52:31 CET 2006


Branko Kokanovic wrote:

> hi all,
> I'm pretty layman on this topic. I have two interfaces, one in local
> network (192.168.0.0) and other to isp. Now, I want to block certain
> mac address from local network from reaching internet, but i want to
> allow him to reach server (for samba, etc...). I tried several
> commands, read on manuals, but all I can get is either all or none
> (either that mac address have internet access and server access, or he
> can't get to internet and server at all ("server" is at 192.168.0.1))
>
> I hope I said all relevant details, if not, ask me and I'll try to tell
>
> Here is my script I use, if that can help a bit:
> ................
> $IPTABLES -P INPUT ACCEPT
> $IPTABLES -F INPUT
> $IPTABLES -P OUTPUT ACCEPT
> $IPTABLES -F OUTPUT
> $IPTABLES -P FORWARD DROP
> $IPTABLES -F FORWARD
> $IPTABLES -t nat -F
>
> $IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state
> ESTABLISHED,RELATED -j ACCEPT
> $IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
> $IPTABLES -A FORWARD -j LOG
>
> $IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE
>
>
> # I tried this
> #iptables -A PREROUTING -t nat -p ALL -m mac --mac-source
> 00:15:F2:33:B5:92 -j DROP

No need for this rule .This drops all packets both inbound for your 
server and outbound through your server to the Internet

> # and this
> #iptables -A FORWARD -p ALL -m mac --mac-source 00:15:F2:33:B5:92 -j DROP

The rule is correct  but it wont match any packets because packets 
matching this mac address are also matching the earlier "-i $INTIF -o 
$EXTIF -j ACCEPT" rule. Just be careful of the flow. Change "-A" to "-I"
HTH,
Jasbir.

>
>
> Thanks in advance, Branko Kokanovic
>
>




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