Iptables and nat [SOLVED]

[cwr]

I've been trying to forward packets from one interface to another, without having to build
a full-scale firewall. Every document I can find says that it's a question of adding
port forwarding and masquerading, but that fails every time for me. The machine has
valid interfaces to each destination, and I can log to the machines each side, but trying
to add forwarding gives me:

[papahuhn]

Seems that your kernel config is not okay after all. However, which networks do you need to route (to)? Maybe you don't need NAT?
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[dE_logics]

There appears to be something wrong with one of --

-A POSTROUTING -o eth0 -j MASQUERADE

How about changing the jump, match and chain to something that is known to work on your system, e.g. drop for, tcp match and -A to input one by one, so you can figure out the missing modules.
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[cwr]

OK, problem solved. I had the "standard" iptables stuff configured in the kernel, but that's
apparently not enough. I went back and added every iptables option in sight and rebuilt
the kernel and it worked.

Thanks for the ideas - Will

[Hu]

The MASQUERADE target is part of NAT and is not standard for a simple packet filter. Enabling that was likely the key.

[cwr]

Yes, at a some point I need to go back and weed out all the obviously irrelevant stuff and
test it again, but for now, it "just works".

Thanks for the tip - Will