dmvpn动态多点vpn（DMVPN dynamic multipoint VPN）.docVIP

dmvpn动态多点vpn（DMVPN dynamic multipoint VPN） Data transmission security using Internet in the IPSec tunnel, is the main solution to the company headquarters and branch communications. Its commercial value, not to mention here, just to find a document is a mccain. The topology of IPSec network can be a star structure (hub? And? Spoke) can also be a net structure (full mesh). In practical application, the data flow is mainly located between the branch and the center, between branch and branch flow distribution is relatively small, so the star structure (hub? And? Spoke) is the most commonly used, and it is more economical. Because the star structure (hub? And? Spoke) (full mesh) network structure than point-to-point link use less, can reduce the cost of lines. In the star topology, branch to branch (spoke? To? Spoke) with no additional communication cost. But in the star structure, branch to branch communication must be across the center, it will cost the center resources and the introduction of delay. Especially in the use of IPSec encryption, decryption center needs to send data in the branch of the tunnel, and re encrypted at receiving data on the branch tunnel. There is a two branch of communications in the same city, and the center in another city, this leads to unnecessary delay. When the star network IPSec (hub? And? Spoke) scale expands unceasingly, the traditional VPN configuration is more complicated, and inconvenient maintenance and troubleshooting. So the dynamic routing of IP packets will be very meaningful. But there is a fundamental problem between the IPSec tunnel and the dynamic routing protocol, dynamic routing protocols rely on multicast or broadcast packets for routing updates, while the IPSec tunnel does not support multicast or broadcast packet encryption. Here we introduced a dynamic multi point VPN (DMVPN) concept. Here will introduce two protocols: GRE and NHRP GRE: generic routing encapsulation. Defined by IETF in RFC 2784. It is a can in an ar