Firewall Wizards mailing list archives

RE: Load Balancing


From: "Daniel Chemko" <dchemko () smgtec com>
Date: Thu, 18 Nov 2004 14:34:17 -0800


I know this is a very easy problem to fix, but I apparently am losing
my 
mind and cannot think.

This question should really be sent to netfilter () lists netfilter org but
I'll bite anyways. 

Because both computers are on the same subnet, the destination computer
will try to directly send the message to the source machine. This'll
break CONNTRACK in Netfilter, and it'll make the packet path look like a
triangle if it works at all. In roder to fix the problem, you'll need to
SNAT the packet on the server as well as DNAT which you're already
doing.

Eg:

iptables -t nat -A PREROUTING --destination $dstpc_fake -j DNAT --to
$dstpc_real

iptables -t nat -A POSTROUTING --destination $dstpc_real --source
$local_net/$local_msk -j SNAT --to $local_fw_ip


You will loose all the source ip specifications on the detination box,
but it's the only way to properly do it.
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