topic Re: NAT thru VPN IPsec in General Topics

NAT thru VPN IPsec

Thomas_B — Tue, 13 Nov 2018 14:22:07 GMT

Hi all,

I come back with my NAT story...

I have a problem.

Please watch the diagram attached.

My site (green) is connected to my customer (violet) thru a VPN IPsec.

My Encryption Domain is my public range (1.1.1.0/28) and the remote Encryption Domain is 9.9.9.0/24.

My Peer is 1.1.1.1 and the remote peer is 20.20.20.20.

VPN are mounted between a CheckPoint and an ASA Cisco 5555.

The CheckPoint is carrying the virtual IP (1.1.1.4) for the NAT of SRV001 with an ARP Proxy.

My customer thru the VPN has to communicate with SRV001 via the NATed IP 1.1.1.4.

Then the check has to NAT it to 192.168.1.100.

On the other sense, SRV001 has to communicate with SRV_CUSTOMERS (9.9.9.8, 9.9.9.9)

When SRV001 initiate the communication, the CheckPoint has to NAT is IP from 192.168.1.100 to 1.1.1.4 and then to send it thru the VPN.

On the other case SRV001 no need to be NATed for corporate communication.

Right now, my VPN Tunnel is UP.

When I am pinging the 9.9.9.8 or 9.9.9.9 with the CheckPoint it's working going thru the VPN Tunnel.

When I am pinging the 9.9.9.8 or 9.9.9.9 from SRV001, I saw with TCPDUMP that the firwall on the customer interface make the NAT and replace the 192.168.1.100 with the 1.1.1.4 but the trafic is not going thru the VPN.

How to force to send the NATed packet thru the VPN?

Support NAT-Traversal is enabled.

I saw the option in the VPN Communities the option "Disable NAT inside the VPN communitie", what is it doing?

Re: NAT thru VPN IPsec

Danny — Tue, 13 Nov 2018 14:36:24 GMT

Thomas wrote "I saw the option in the VPN Communities the option "Disable NAT inside the VPN communitie", what is it doing?"

Star Community Properties > Advanced VPN Properties

Disable NAT inside the VPN community

Even if NAT is configured it is possible to disable NAT inside the VPN community. If NAT is disabled, when a host behind a community member opens a connection with another host behind a community member, the original IP addresses are used. Other connections use the translated address.

Note: This option for disabling NAT applies to hide NAT only, not static NAT.

Re: NAT thru VPN IPsec

Enrique — Mon, 21 Oct 2019 11:35:25 GMT

I'm not sure about this, but I would try to modify your local encryption domain to match your local network (192.168.1.0/24). Or at least add the original SRV001 IP address (192.168.1.100) to the encryption domain.

BR,