Dynamic Multipoint VPN (DMVPN) enables better scaling of large and small IPsec VPNs by combining generic routing encapsulation (GRE) tunnels, IP Security (IPsec) encryption, and Next Hop Resolution Protocol (NHRP) routing. Security Manager supports DMVPN using the EIGRP, OSPF, and RIPv2 dynamic routing protocols, and GRE static routes. In addition, On-Demand Routing (ODR) is supported. ODR is not a routing protocol. It may be used in a hub-and-spoke VPN topology when the spoke routers do not connect to any router other than the hub. If you are running dynamic protocols, ODR is not suitable for your network environment.