Introduction to NAT

NAT, the abbreviation for Network Address Translation, is the protocol to translate the IP address within an IP packet header to another IP address. When the IP packets pass through the security appliances or routers, the appliances or routers will translate the source IP address and/or the destination IP address in the IP packets.  In practice, NAT is mostly used to allow the private network to access the public network, or vice versa.

The Hillstone devices achieve the NAT function through the creation and implementation of NAT rules. There are two types of NAT rules, which are source NAT rules (SNAT Rule) and destination NAT rules (DNAT Rule). SNAT translates source IP addresses, thereby hiding the internal IP addresses or sharing the limited IP addresses; DNAT translates destination IP addresses, usually translating IP addresses of internal servers (such as the WWW server or SMTP server) protected by the device to public IP addresses.