From getting started to being proficient in hacker linux, Ma Hao handled the VPN Server agenda in three minutes :. VPN introduction. how VPN works. VPN data transmission protocol. VPN Server construction case: Company X has a long distance between departments, and the company's network cannot accommodate a LAN, to ensure secure transmission and easy management of information in each LAN, what are your best methods as system administrators? Solution: 1. Set up a dedicated line between each LAN and establish a point-to-point connection to form a wide area network. 2. Establish a Virtual Private Network Using VPN technology. VPNVPN is short for virtual private network. It is a private network built on a public network. When you use a private network, it feels like a network connected by a VPC. Its transmission channel is private and independent, however, the actual data is transmitted through the public network and thus becomes a virtual private network. Key Technologies of VPN. security tunnel technology. encryption technology. authentication VPN data transmission protocol pptp. IP-based Interconnection Network. no header compression. no tunneling authentication. use PPP to encrypt L2tp. based on a variety of WAN connections, media such as frame relay, IP, X.25. header compression. tunnel authentication. use IPSec to encrypt client ----- PPTP/L2TP ------ server VPN security protocol (1) PPTP ---- point to point tunnel protocal (point-to-point Tunneling Protocol) data communication over the Internet, to encapsulate and encrypt data streams, PPTP can implement these two functions and implement multi-function communication over the Internet. VPN security protocol (ii) L2TP ---- layer2 tunneling protocol (Layer 2 tunnel protocol) PPTP is very similar to L2TP, because a part of L2TP is the PPTP protocol, both protocols allow the customer to establish a tunnel through the network. L2TP also supports channel authentication. Benefits of Using VPN (1) reduce costs. (2) enhanced security. (3) network protocol support. (4) ip address security.