iptables intercept local traffic

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http://serverfault.com – i hope someone can help me out with somewhat simple task. I'm trying to redirect a client in my router through my desktop PC, so i can dump the traffic and analyze it (its potential source of poisoning the network with malicious packets). However i don't have a second NIC on my hands and i was hoping i can redirect all the traffic from that IP through my PC. In essence to become MITM for the client. Does anyone have any idea where to start: Current state: (localip)->(router)->(internet) And what i want to do: (localip)->(pc)->(router)->(internet) (HowTos)