Reference:Configuration/ETH/NAT

Use of NAT (Network Address Translation) for the relevant interface can be enabled here. It is also possible to exclude particular network addresses and masks from the translation.

• Include Interface in NAT: A checked check box enables NAT for the interface, providing NAT was enabled in general under chapter "Configuration/IP/NAT". In other words, the network connected to ETHn is regarded as external unless it was excluded under Exclude Address or Exclude Mask.
• Exclude Address: IP network that should not be included in the Network Address Translation.
• Exclude Mask: IP network area that should not be included in the Network Address Translation.