DMVPN Overview
DMVPN ・mGRE + NHRP + IPsec Protection
DMVPN Phase 1/2/3
・Phase 1 ・Hub makes multipoint GRE tunnels into each Spokes. ・Spokes make GRE tunnel only with Hub. ・Spokes must transit their traffic via Hub.
・Phase 2 ・Hub and Spokes make multipoint GRE tunnels each other. ・Spokes have other spoke's address as Next-Hop. ・Spokes can transit traffic to other spoke directly.
・Phase 3 ・Hub and Spokes make multipoint GRE tunnels each other. ・Spokes have only Hub's address as Next-Hop, so they can summarise address. ・Spokes make multipoint GRE tunnel into other spoke
using ip nhrp redirect packet sent from Hub, they can transit their traffic to other spoke directly.
