Weird nat (PIX 6.3.3)

Feb 28, 2006 1 Replies

Hello, here is the scenario,



Site in Paris:



external IP of the PIX: 195.238.14.14/28 internal IP of the PIX 192.168.10.1/25



Site in Madrid:



external IP of the PIX: 212.217.67.87/29 internal IP of the PIX: 10.10.10.1/25



Ok, the subnet in Paris has to show up in Madrid as 192.168.10.2, this ip begets the source ip of any packets going through a VPN to reach any devices in Madrid.



How do I do it?



I understand I need,



Same phase 1 and phase 2 on both sites,



on Paris, I need a nat0 access list like



access-list nat0 permit ip 192.168.10.2 255.255.255.255 10.10.10.0



255.255.255.128

an access-list that is going to match the crypto-map, like



access-list mymap permit ip 192.168.10.2 255.255.255.255 10.10.10.0



255.255.255.128

on Madrid, I need an access-list nat0



access-list nat0 permit ip 10.10.10.0 255.255.255.128 host 192.168.10.2



and



access-list mymap permit ip 10.10.10.0 255.255.255.128 host 192.168.10.2



My question is, how do I hide-nat Paris to make sure the traffic will not be "nat 1 (inside)" to the external IP address of the firewall for web browsing? I am afraid, there is like a race condition between the nat0 and the nat 1.



Would you tell me more on that?



Thank you,



Alfred


see below

There is no race condition , nat 0 (inside) is always processed first.

So all lines in your crypto acl must be added to the nat0 acl. Once the packet is triggered by nat 0 (inside) , it will not be NATed and will continu to the crypto engine. Traffic not defined in nat 0 (inside) will continu in the nat process, and if it's triggered by nat 1 (inside) it will be nated accordingly.

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