[olug] Application problem with NATing

[Jeff Hinrichs]

1 to 1 NAT (http://www.lug.udel.edu/articles/firewall-1to1nat/1to1nat.html)
OR
If the app behind the firewall/NAT is something that you have written, you
could use a blind-drop (http://www.pbs.org/benfranklin/l3_world_spies.html)
method to establish an out of band signal
(http://www.iec.org/online/tutorials/ss7/topic02.html) from the client to
the server.  I've never seen anything written about it with regards to
computer connectivity but I've used it a number of times to over come this
exact problem.

In a nutshell: you set up an out of band communications link from the client
to the server.  The server, on a regular schedule checks for a signal
somewhere outside the firewall, when it sees the signal it attempts to
establish a connection with the client.  When the client wants to connect to
the server it leaves a signal at the agreed upon "drop box" and waits for
the server to attempt contact.  It is also possible to write a server side
drop box monitor that does the drop box check and then tells the server to
connect to the client.


----- Original Message ----- 
From: "Craig Wolf" <cjwolf at mpsomaha.org>
To: <olug at olug.org>
Sent: Saturday, February 07, 2004 7:09 PM
Subject: [olug] Application problem with NATing


I have a program that connects back to a Unix system (this part is not that
important).  The problem it has is that it has problems with connecting to a
private IP behind my nat'ed firewall.  How could I fool the app into
thinking that there IS no firewall?
I will not be able to get too many details until Monday morning...

Any and all help/ideas would be GREATLY appreciated.

Craig Wolf
Linux Web Server Support
Desktop/Network Specialist
402-894-6283

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