Scenario 3 - How To Configure Nat If You Have Internet-Facing Public Servers; Application Scenario - ZyXEL Communications ZyWALL USG 20 User Manual

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– ZyWALL USG Support Notes
Scenario 3 — How to configure NAT if you have Internet-facing public servers

3.1 Application Scenario

It is a common practice to place company servers behind the USG's protection; while at the same time letting WAN side clients/servers access the intranet
servers. To give an example, the company may have an internal FTP server, which needs to be accessible from the Internet as well. To fulfill this requirement,
user can configure a NAT mapping rule to forward the traffic from Internet side to intranet side. This feature can not only ensure service availability but also
helps avoid exposing the server's real IP address to be attacked.
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