SonicWALL TZ 190 Manuale Utente

Chapter 21: 

The Network Address Translation (NAT) engine in SonicOS Enhanced allows users to define 
granular NAT polices for their incoming and outgoing traffic. By default, the SonicWALL security 
appliance has a preconfigured NAT policy to allow all systems connected to the LAN interface 
to perform 

 

many-to-one NAT using the IP address of the WAN interface, and a policy to not perform NAT 
when traffic crosses between the other interfaces. This chapter explains how to set up the most 
common NAT policies.

Understanding how to use NAT policies starts with an the construction of an IP packet. Every 
packet contains addressing information that allows the packet to get to its destination, and for 
the destination to respond to the original requester. The packet contains (among other things) 
the requester’s IP address, the protocol information of the requestor, and the destination’s IP 
address. The NAT Policies engine in SonicOS Enhanced can inspect the relevant portions of 
the packet and can dynamically rewrite the information in specified fields for incoming, as well 
as outgoing traffic.

You can add up to 512 NAT Policies on a SonicWALL security appliance running SonicOS 
Enhanced, and they can be as granular as you need. It’s also possible to create multiple NAT 
policies for the same object – for instance, you can specify that an internal server use one IP 
address when accessing Telnet servers, and to use a totally different IP address for all other 
protocols. Because the NAT engine in SonicOS Enhanced supports inbound port forwarding, it 
is possible to hide multiple internal servers off the WAN IP address of the SonicWALL security 
appliance. The more granular the NAT Policy, the more precedence it takes.