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Network Address TranslationΒΆ

Network Address Translation, or NAT, involves changing properties of a packet as it passes through a router. Typically this is done to mask or alter the source or destination to manipulate how such packets are processed by other hosts.

The most common examples are:

  • Source NAT, also known as Outbound NAT, which translates the source address and port of a packet to mask its origin.

  • Destination NAT, commonly referred to as Static NAT or Port Forwards which translate the destination address and port of a packet to redirect the packet to a different target host behind the router.

TNSR applies NAT based on the configured mode and the presence of directives that set inside (internal/local) and outside (external/remote) interfaces.

An inside interface is a local interface where traffic enters and it will have its source hidden by NAT. An outside interface is an interface where that translation will occur as a packet exits TNSR. An example of this is shown in Outbound NAT.


NAT is processed after ACL rules. For more information, see ACL and NAT Interaction.


NAT-specific virtual reassembly parameters have been deprecated in favor of shallow virtual reassembly. See IP Reassembly.