Private line VPN line, this "special" is mainly reflected in the dedicated IP, after connecting to the VPN, the export IP obtained is unique. VPN is Virtual Private Network (Virtual Private Network, VPN for short) refers to the technology of establishing a private network on a public network. The reason why it is called a virtual network is mainly because the connection between any two nodes of the entire VPN network does not have the end-to-end physical link required by the traditional private network, but is built on the network provided by the public network service provider. Platforms, such as the logical network on the Internet, ATM (Asynchronous Transfer Mode), Frame Relay (Frame Relay), etc. User data is transmitted in logical links. It covers encapsulation, encryption, and identity across shared or public networks To verify the expansion of the linked private network. VPN mainly uses tunneling technology, encryption and decryption technology, key management technology and user and device identity authentication technology.