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Passing IPSec VPN traffic through a Port-masquerading firewall



Howdy,

    I need to support IPSec VPN users through Linux masquerading firewall.
The linux masquerade code converts the "client-side" IP addresses into its
address, and manipulates the source port in order to
keep track of who is doing what so it can demasquerade on the way back.  

   Now, I understand that there are two parts to the VPN protocol - the
initial key exchange at port 500,
and then the ESP packets.   I know that there are multiple-IP-address NAT
devices that work with this
method, so I assume that I can change the IP address of the packets without
getting into too much
trouble.   But I have been told that there is no session number that I can
draw off of to distinguish two clients creating VPN tunnels to the same
destination server.

  I have looked at the RFC for ESP, and it seems to support this claim.  I
was wondering if I could
potentially use the sequence number as a reasonably unique identifier - Not
perfect, but perhaps
ok.  Does anyone on this list have any other suggestions?

	Thanks
		John


-------
johnbr@elastic.com		- John Brothers	- 	(678) 297 3084



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