Network Address Translation (NAT)

Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations.  NAT serves three main purposes:

• Provides a type of firewall by hiding internal IP addresses.
• Enables a company to use more internal IP addresses. Since they're used internally only, there's no possibility of conflict with IP addresses used by other companies and organizations.
• Allows a company to combine multiple ISDN connections into a single Internet connection.

Important

• It is important to select network interface to be NAT Provider and public IP address for external (Internet) traffic.  
• It is necessary to define internal network subnets which traffic must be provided to external network.
• Don't change public IP address for NAT manually if it is not necessary for proper NAT working.