• DMVPN Phase 1
    • mGRE on Hub and p-pGRE on spokes
      • No direct spoke to spoke communication.
    • Routing
      • Summarization and default at hub is allowed.
      • Next-hop on spokes is always changed by the hub.
  • DMVPN Phase 2
    • mGRE on hub and spokes
      • NHRP required for spoke registration to hub.
      • NHRP required for spoke to spoke resolution.
      • Spoke to spoke tunnel triggered by spoke.
    • Routing
      • Summarization/default not allowed at hub.
      • Next hop on spokes is always preserved by hub.
      • Multi-level hierarchy requires hub daisy-chaining.
  • DMVPN Phase 3
    • mGRE on hub and spokes.
      • NHRP required for spoke registration to hub.
      • NHRP required for spoke to spoke resolution.
    • When a hub hairpins out same interface:
      • Send NHRP redirect message to packet source.
      • Forward original packet down to spoke via RIB.
    • Routing
      • Summarization and default at hub is recommended.
        • Results in NHRP routes for spoke to spoke tunnel.
        • With no-summary, NHO is performed for spoke to spoke tunnel.
          • Next-hop is changed from hub IP to spoke IP.
      • Next hop on spokes is always changed by the hub
        • NHRP resolution triggered by hub.
      • Multi-level hierarchy works without daisy-chaining.

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