Port forwarding revisited

[ddm at mclinux.com (Derek D. Martin)]

Bill Horne said:

> However, I also have a VPN client on one of my internal machines (call
> it Omega for illustration), in order to access Verizon's network from
> home. This client works OK when Omega is connected directly to the cable
> modem, but can't originate a connection when the Linux box is doing
> masquerading.

IPSec is not designed to work with NAT, however some implementations
of VPN software that use IPSec have hacks to make it work.  For
example, the Cisco VPN concentrator has a -n option on the Linux
client (and a check box on the Windows client) to enable NAT
transparency.  I have no idea what software you're using, so I can't
tell you what to do.

There are also patches to the Linux kernel that help make this work if
your client doesn't do it for you, but I have little knowledge of them
so I can't offer much help there.  You might try poking around at
www.freeswan.org for some hints...  And I've also heard that they
don't work reliably, but I don't know.

You might also try posting this question on GNHLUG, as there are a
couple of people there who may have answers.  You might also mention
what software you're using...

-- 
Derek Martin
Senior System Administrator
Mission Critical Linux
martin at MissionCriticalLinux.com

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