i just did a similar setup on a powertower with my cable serviceand i
used the IPNAT how to in the online netBSD manual

http://www.mclink.it/personal/MG2508/nbsdeng/chap-net.html#SECT-IPNAT

just forget about any of the ppp specific settings and it should just
work fine. i dont have access to my machine right now so i cant look it
up, but if you run into more trouble i can tonight

-Jojo

>OK that's probably not the right question since there must be a bunch 
>of DSL'ers who are doing something similar.  I'm trying to use NAT on 
>an Mac 7500 with a PCI D-Link Ehternet card as well as the built-in. 
>Modifying one of the example files I now have:
>
>macbsd# ipnat -l
>List of active MAP/Redirect filters:
>map rtk0 192.168.5.0/24  -> 137.78.218.53/32  portmap tcp/udp 40000:60000
>map rtk0 192.168.5.0/24  -> 137.78.218.53/32
>map rtk0 192.168.5.0/24  -> 137.78.218.53/32  proxy port ftp ftp/tcp
>
>List of active sessions:
>macbsd# uname -a
>NetBSD macbsd 1.5_ALPHA NetBSD 1.5_ALPHA (GENERIC) #8: Thu Jun 22 
>10:44:11 PDT 2000     matt@yosemite.local:/other/kobj/macppc/GENERIC 
>macppc
>macbsd# ifconfig -a
>rtk0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         address: 00:50:ba:43:d2:77
>         media: Ethernet autoselect (100baseTX full-duplex)
>         status: active
>         inet 137.78.218.53 netmask 0xffffff00 broadcast 137.78.218.255
>         inet6 fe80::250:baff:fe43:d277%rtk0 prefixlen 64 scopeid 0x1
>mc0: flags=8863<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         address: 00:a0:40:20:f6:61
>         media: Ethernet manual
>         inet 192.168.5.1 netmask 0xffffff00 broadcast 192.168.5.255
>         inet6 fe80::2a0:40ff:fe20:f661%mc0 prefixlen 64 scopeid 0x2
>lo0: flags=8009<UP,LOOPBACK,MULTICAST> mtu 32972
>         inet 127.0.0.1 netmask 0xff000000
>         inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3
>         inet6 ::1 prefixlen 128
>....
>
>I can ping this box from either interface, but I can't ping through 
>it from the 192.168.. subnet on mc0.  I'm fairly sure that I tried 
>pinging the 137.78.218.53 address from there as well and it worked. 
>(Will double check.)
>
>Either I'm doing something obvious and stupid or else I just need to 
>upgrade to 1.5.  I wanted to get a similar box working on the subnet 
>first, but I can't do the install there the way I intended without 
>getting NAT going first.
>
>Signature held pending an ISO 9000 compliant
>signature design and approval process.
>h.b.hotz@jpl.nasa.gov, or hbhotz@oxy.edu
>