What is the difference between Virtual Server and 1:1 NAT?

Zyxel_Emily

Question
I would like to use NAT feature to publish an internal server for external users. On the NAT Add/Edit page, there are Virtual Server and 1:1 NAT. Which one should I choose? What is the difference between Virtual Server and 1:1 NAT?

Answer

Both Virtual Server and 1:1 NAT are able to publish internal servers to Internet.

The difference between Virtual Server and 1:1 NAT is that 1:1 NAT has an additional SNAT (source NAT) while Virtual Server does not.

Configuration
In this example, create a NAT rule and select 1:1 NAT. 

Original IP: 61.222.75.17

Mapped IP: 192.168.1.33

Then the outgoing interface for the server 192.168.1.33 uses 61.222.75.17 to access Internet.

Test Result

You can check SNAT flow In MAINTENANCE > Packet Flow Explre > SNAT Status.

The source IP 192.168.1.33 access to Internet with a SNAT routing. The outgoing address will be replaced by Original IP 61.222.75.17.