Still have a problem with my ipnat.conf file

I am running netbsd 1.5.2

This is my ipnat.conf file

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# /etc/ipnat.conf

map rtk0 192.168.1.0/24 -> 0/32 proxy port ftp ftp/tcp
map rtk0 192.168.1.0/24 -> 0/32 portmap tcp/udp 40000:60000
map rtk0 192.168.1.0/24 -> 0/32

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It looks very similar to ones I see all over the net, the only difference being the rtk0 and the lack of a desitination ip address.

Someone please help!