How to make iptables DNAT work with macvlan

I'm stuck with an AT&T gateway that doesn't understand a MAC can have more than 1 IP address. So I'm using macvlan on linux to add ports with different mac addresses.

This seem to work for local connections to the macvlan ports. But, when I try and DNAT them into a private DMZ the packets seem to disappear. I have ip_forwarding turned on and other outgoing packet forwarding is working.

I've used tcpdump and trace in iptables to no avail. The DNAT rule fires, then the packets never emerge anywhere.

I'm running Centos 6.3.

I finally solved this. Turns out all the wacky network shenanigans caused by trying to forward macvlan traffic tripped up the kernel reverse path filter causing it to drop the packets. I had to set rp_filter = 0 for any interface the traffic traversed.