Perform the following tasks to configure various aspects of NAT. In addition to the examples below, there are examples in the section NAT Configuration Examples.
The first three NAT examples in this section are based on the following topology:
Based on this topology, there are three NAT policies we need to create as follows:
- To enable the clients on the internal network to access resources on the Internet, the internal 192.168.1.0 addresses will need to be translated to publicly routable addresses. In this case, we will configure source NAT (the purple enclosure and arrow above), using the egress interface address, 203.0.113.100, as the source address in all packets that leave the firewall from the internal zone. See Translate Internal Client IP Addresses to Your Public IP Address (Source DIPP NAT) for instructions.
- To enable clients on the internal network to access the public web server in the DMZ zone, we must configure a NAT rule that redirects the packet from the external network, where the original routing table lookup will determine it should go based on the destination address of 203.0.113.11 within the packet, to the actual address of the web server on the DMZ network of 10.1.1.11. To do this you must create a NAT rule from the trust zone (where the source address in the packet is) to the untrust zone (where the original destination address is) to translate the destination address to an address in the DMZ zone. This type of destination NAT is calledU-Turn NAT(the yellow enclosure and arrow above). See Enable Clients on the Internal Network to Access your Public Servers (Destination U-Turn NAT) for instructions.
- To enable the web server—which has both a private IP address on the DMZ network and a public-facing address for access by external users—to both send and receive requests, the firewall must translate the incoming packets from the public IP address to the private IP address and the outgoing packets from the private IP address to the public IP address. On the firewall, you can accomplish this with a single bi-directional static source NAT policy (the green enclosure and arrow above). See Enable Bi-Directional Address Translation for Your Public-Facing Servers (Static Source NAT).
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