[Openswan Users] Odd NAT behavior with roadwarrior config

Jacco de Leeuw jacco2 at dds.nl
Fri Aug 18 11:22:02 EDT 2006

Rick Romero wrote:

> I've got a single box on the internet with two interfaces, but I'm not 
> using interface 2. I just want to create a vpn tunnel to my subnet.

You mean you've got two interfaces, both interface 1 (external) and
interface 2 (internal) are up but there is no cable connected to
interface 2? That should not be a problem.

> I followed Nate Carlson's ipsec-l2tp page, and it's working 99% ;)

I'm afraid Nate's webpage is not 100% correct, in particular when
NAT is involved.

> I'm able to make a secure connection, ping both the internal and 
> external interface, I can even ping anything on the internet.
> I can do an nslookup, and I can also telnet to any box on the internet, 
> BUT I cannot combine the two :)   So, for example, I can:
>   telnet  25
> but I can't
>   telnet mail.havokmon.com 25
> even though I can do an nslookup.

Perhaps it's this problem?

Either way, I suspect that it is a Windows network issue. If you
run tcpdump you should be able to see what DNS request are sent
through the connection:

tcpdump -n -l -i ppp0 udp port 53

Jacco de Leeuw                         mailto:jacco2 at dds.nl
Zaandam, The Netherlands           http://www.jacco2.dds.nl

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