Meaning of the destination NAT on the USG2000 and USG5000

The Network Address Translation (NAT) is an address translation technology. It can convert the address in an IPv4 packet header to another address. Generally, the NAT is used to convert a private IP address in the IPv4 packet header to a public IP address, so that multiple users on the private network can access the Internet using less public IP addresses. Therefore, the NAT technology can address the IPv4 public address shortage issue caused by the expansion of the Internet scale.

The source NAT indicates that the source address in a packet is converted. The source NAT modes implemented in different application scenarios are different.

USG firewalls do not support NAT based on domain names accessed by intranet users. To allow users to access specified websites, you can configure the URL filtering.

Based on application scenarios, the NAT can be categorized as source NAT, server mapping, and destination NAT.

The Generic Routing Encapsulation (GRE) protocol encapsulates data packets of certain network-layer protocols, so that the encapsulated packets can travel through another network-layer protocol. GRE is one of the tunneling technologies and is an L3 tunneling protocol. The GRE provides a transmission path for encapsulated packets by establishing a virtual point-to-point connection.