Meaning of the source NAT on the USG2000 and USG5000

The server mapping is classified into static mapping and server load balancing. The static mapping is a type of one-to-one mapping, that is, a public IP address corresponds to an intranet server. The server load balancing is a type of one-to-many mapping. It can distribute traffic generated by external network users for accessing the intranet servers among specific intranet servers based on a certain algorithm.

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 destination NAT is mainly used to modify the destination gateway address when a mobile device user accesses the Internet.

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.