To understand the principles of DMVPN Phase I, remember these facts:
- Spokes use point-to-point GRE tunnels;
- Hub site has multipoint GRE tunnel;
- All the traffic flows through the hub site;
- The next-hop for routes received over DMVPN must be the hub site;
- NHRP is used by the hub site to get spokes’ tunnel endpoint addresses.
- Spoke sites use NHRP just to register with the hub site.