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Date:      Mon, 8 Nov 2004 00:07:57 +0100
From:      Noses <>
To:        ipfw-mailings <>
Subject:   nat + forwarding == routing error???
Message-ID:  <>

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I've got a slightly complicated problem. I'm running a router with 
multiple outgoing connections and a number of LANs and a DMZ being 
routed through it.

1) Even though I have "fwd <appropriate router>" rules for all 
addresses I have to have a default router or the rules won't even be 
reached (giving me a "no route to host" - I'd assume there should be a 
way to force a packet to get into ipfw even if the kernel is believing 
the packet would go nowhere.

2) Strangest problem: It depends on passing through natd whether a fwd 
rule is behaving according to the man page or not. I've got the 
following construction:

divert ${NAT_1} all from to any in via ${nic_LAN}
fwd ${Provider_1} all from ${DMZ_Provider_1} to any not ${local}
fwd ${Provider_1} all from ${NAT_addr_1} to any not ${local}

The relevant NATD is using an "alias_address" statement (if there is 
any difference). Extending the rules by "log" statements shows packets 
being caught by the correct rules and tcpdump shows the packets on the 
wire having been treated correctly by NAT.
Now packets from DMZ_Provider_1 are being sent to the correct outgoing 
interface (which is different from the default route's interface) but 
the packets that have been aliased by natd are sent out on the default 
route even though the log shows me that the relevant "fwd" rule has 
been taken.

Any ideas? I always assumed that the knowledge about packets having 
been treated by NAT would be kept inside natd...


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