[Jeff Gilles]

I've been trying off and on for several days to get ipf installed on my
Solaris 8 box to test out a particular configuration.  I had previously
convinced myself from reading the howto that my application could be
accomplished, but now I'm not so sure.  If anyone who is much more
intimate with this than I am could guide me along, I'd appreciate it.
The crux of the issue is whether I can use ipf/ipnat to change the
destination address of an outbound packet and the source address of an
inbound packet.  This is kind of the opposite of what traditional NAT does.
Here's the long story.  I have a Sun Ultra 10 running Solaris 8 which is
running a large software application.  This application communicates
through a large IP network to a board running VxWorks which resides in a
compact PCI shelf.  This card in turn communicates through a private IP
network (over a compactPCI midplane) to other VxWorks cards using their
private IP addresses.  Certain software requires the Sun to directly
address the privately addressed cards by using the main card as a
router.  Here's the picture:
Sun                            VxWorks
                             main board
hme0                             if1
192.168.0.9 ----(IP cloud)----192.168.100.1
                              routes to           other VxWorks
                                if2                   board
                             10.20.1.20-------------10.20.1.7
So the routers in the IP cloud know that to get to 10.20.1.0 subnet, the
packet needs to go through the "router" 192.168.100.1.
Now, I have a situation where the routing in the IP cloud cannot/will
not be done, so I am trying to find a workaround.
My idea was to get extra addresses on the 192.168.100.x subnet to use as
aliases for the private addresses.  Let's say that I have 192.168.100.7
as an alias for 10.20.1.7.  The software application on the Sun would
try to send its packet to 10.20.1.7, and I'd like to use ipnat to change
the destination from 10.20.1.7 to 192.168.100.7.  The packet then gets
sent out and routed across the network to a newly inserted device which
has an ethernet port on the 192.168.100.x network with 192.168.100.7 as
an IP.  It would use ipnat to change that back to 10.20.1.7, and send it
out a second port over to 192.168.100.1.
Visually:
Sun                             VxWorks
                              main board
hme0                              if1
192.168.0.9-----(IP cloud)-[ ]--192.168.100.1
           ^               ^   routes to            other VxWorks
           |               |     if2                   board
           |               |  10.20.1.20-------------10.20.1.7
       run ipnat           |
         here           new device
      to change         runs ipnat
      destination       here to change
                         origin
So is this the type of application that ipf/ipnat can do gracefully and
simply?  Or is this in some profound way different than all of the other
applications I've been reading about in the various documentation and
emails on the subject?
Thanks,
Jeff Gilles
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