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I have a site-to-site VPN set up with a vendor. Let's say the tunnel endpoints are on my side and on the vendor's side (which get's NATted to their LAN of 10.x.x.x). This is working fine, I have a SonicWall and I have a VPN policy setup so traffic to 192.1.2.x from my side goes through their VPN and reaches the correct hosts.

The problem is I have an (old, unmodifiable) application that is trying to connect to on their network. If I can make this go through the VPN as if it were, then it would reach the correct destination. The vendor is unwilling to add as a tunnel endpoint.

I tried a NAT policy to transform traffic towards to, but I believe that doesn't also send it through the VPN because NAT is applied to traffic as it leaves the firewall and after the point where it would have triggered the VPN routing rule. Basically I want to take any traffic to, change its destination to, and send it through the VPN tunnel for I'm not an expert at firewall config, can someone point me in the right direction?

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What type of Sonicwall do you have? – Nixphoe Jul 24 '11 at 18:26

As well as NATing the traffic did you loop it back to your LAN? You might try using a loop back connection with better results. After that it should be routed to your VPN.

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hey, i can't figure out how to loop it back while keeping the destination so that it routes to the VPN – dan Jul 25 '11 at 17:55

I would stay the NAT rule to rewrite the destination is a good start. To be honest, I would have thought that would be sufficient. Are you certain that traffic is actually hitting your firewall? I assume you don't have a local 10.x.x.x network that these packets are going to.

Other things to try may be a manual routing policy. You could send all 10.x.x.x traffic through your VPN tunnel interface. Also, try setting the VPN as the exit interface on that NAT rule.

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i only have 192.x networks.. i think the only way to make the vpn interface be selectable in the NAT rule is to change the VPN from site-to-site to 'tunnel interface'. I tried that late at night, but couldn't get it to connect to the vendor..I'll read up more on the docs and try again – dan Jul 25 '11 at 18:05

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