Hi Sascha,

Here is an example for PIX part:
http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a00800949f1.shtml

Topology:
---------
(192.168.4.0/24)PIX <--Internet--> VPN concentrator*(192.168.4.0/24)

*Instead of the Checkpoint it is a VPN concentrator at the other side, but this 
is no matter now.

Come back with the result, if possible.

Cheers,
Akos

-----Original Message-----
From: Mailing list for discussion of Firewall-1 [mailto:[EMAIL PROTECTED] On 
Behalf Of cisco4ng
Sent: 2007. április 15. 18:00
To: [EMAIL PROTECTED]
Subject: Re: [FW-1] Another VPN and NAT question

Hi Sascha,

I think it is better if I can illustrate with an example:

FWa has internal network of 192.168.1.0/24.  FWa is a CP firewall FWb has 
internal network of 192.168.2.0/24.  FWb is a CP firewall FWc has internal 
network of 192.168.2.0/24.  FWc is a Pix firewall.

you have site-to-site vpn between FWa and FWb.  No problem so far.  Now you are 
trying to establish site-2-site vpn between FWa and FWc.  Problem indeed.

Solution:

NAT the internal network of FWa from 192.168.1.0/24 to 10.1.1.0/24.  In other 
words, in the encryption domain of FWa, you will have two networks:  
192.168.1.0/24 and 10.1.1.0/24.  When you define an Inter-Operable Device for 
the Cisco Pix, you will have to include network 10.1.2.0/24 in the remote 
encryption domain.

In the address translation tab, do this:

source                dest               translate source         trans 
destination
192.168.1.0/24    10.1.2.0/24     10.1.1.0/24                original
10.1.2.0/24         10.1.1.0/24     original                      192.168.1.0/24

On the Cisco Pix side,  the  reverse is true.  It is called policy nat on the 
pix side.

In summary, from FWA, when you want to communicate with network behind the 
Cisco Pix, you will NAT the source to 10.1.1.0/24 and the destination will be 
10.1.2.0/24.  On the Pix side, the source will be 10.1.2.0/24 and destination 
will be 10.1.1.0/24.  NO ip address of 192.168.x.0/24 will exist anywhere 
inside the VPN tunnel.

Hope that makes sense to you.

cisco4ng

Sascha Picchiantano <[EMAIL PROTECTED]> wrote: Hi,

closely related to the other question I asked a couple of days ago, I was just 
thinking about how to configure a site-to-site VPN if the remote peer uses IP 
addresses that I already use in another VPN. I guess I could just NAT his 
address range to whatever I like and I can work with, but what I can't figure 
out is what I would put into the encryption domain of the remote end's gateway 
object. His original addresses or the NAT addresses I defined?

I figure that if I use the original addressses, it might not work because I 
already have these addresses in another encryption domain and VPN-1 could not 
decide which VPN to use...? But if I use the NAT addresses, wouldn't I see tons 
of "no valid SA" entries in my log because within the VPN tunnel the IP 
addresses are different than those in the enc domain...?

Confusing. Hope my thoughts make sense to you and you can give me some 
enlightment :)

Cheers
Sascha

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