[Openswan Users] NAT-T and left=%defaultroute

Paul Wouters paul at xelerance.com
Thu Sep 22 17:58:56 EDT 2011

On Thu, 22 Sep 2011, Simon Chan wrote:

> I am trying to learn Openswan, starting with a simple NAT'ed setup.
> One end is behind a cable modem Nat router. The other end is not Nat'ed.
> All the examples I can find tell me to use "left=%defaultroute" which works. If I replace %defaultroute with the real public IP or the cable
> modem's IP (192.168.x.1) then I get error:
> "We cannot identify ourselves with either end of this connection."

If you have a static ip behind NAT, you can use left=a.b.c.d
If you have a dynamic IP, you use left=%defaultroute and openswan will pick
the IP that seems to be the one used to communicate to the world based on
your default route.

> conn office
>         authby=secret
>         left=%defaultroute
>         leftid=
>         leftsourceip=
>         leftsubnet=

All your 20 connections have different subnets?

>         right=216.x.x.x
>         rightsubnet=
>         auto=route


You also need something along the lines of: iptables -I POSTROUTING -s -d -j RETURN


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