1558 CHAPTER 80: DVPN C ONFIGURATIONVAM clientVAM clients are the nodes comprising a DVPN. A VAM client registers its privateaddress, public address, and VAM ID with the VAM server and inquires of the VAMserver concerning information about other VAM clients. Unless otherwise noted,the term “VAN client” in this document refers to a Hub or Spoke.HubA Hub is a type of VAM client. As the central device of a VPN, it is the exchangecenter of routing information. The Hub in a Hub-Spoke network is also the dataforwarding center.SpokeA Spoke is a type of VAM client. Usually acting as the gateway of a branch office,a Spoke does not forward data received from other DVPN nodes.AAA serverAn authentication, authorization, and accounting (AAA) server is used for userauthentication and accounting.Operation of DVPN DVPN employs the client/server model. Operating at the application layer of theTCP/IP protocol stack, DVPN uses UDP as its transport layer protocol. A DVPNconsists of one server and multiple clients. The public address of the server in aDVPN must be static. The private address of a client needs to be assigned inadvance, while the public address of a client can be manually configured ordynamically assigned. All the private addresses of the clients (including all Hubsand Spokes) of a DVPN must belong to the same network segment.Each client registers the mapping of its private address and public address with theserver. After clients register their address mappings with the server, sessions areautomatically established between them. Each client uses the VAM protocol tocommunicate with the server and uses the DVPN tunneling protocol to establish,maintain, and remove tunnels between itself and another client. Whenever thereis a change in the number of nodes, the server will be notified automatically andwill then notify the change to all online clients in turn so that the tunnels arerefreshed synchronously.
