In this series, I'm going to explain all three phases of DMVPN. DMVPN should be thought of as a routing technology and not necessarily a security one. Yes, you can encrypt these VPN tunnels but DMVPN is more like dynamically created GRE tunnels with the use of NHRP. The encryption, while not mandatory, is typically used to secure the encapsulated traffic across the public internet. An important note, I find the naming Phase 1, 2 and 3 is very confusing as it clearly can get confused with IPsec Phases. A better way to think of is DMVPN Type 1, 2 and 3 were each type represents a different configuration and behavior. Throughout this post, I'm going to use the same topology below.