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RS0016 - NHRP Phase 2 and 3

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The video continues from "RS0015 - NHRP Phase 1" video into Phase 2 and 3 with dynamic Spoke-to-Spoke tunnels. We observes how a spoke router is able to construct a direct tunnel to other spokes through the process of Resolution request and reply. In the second half, the video demonstrates the benifit of route summarization allowed by NHRP Phase 3 configuration. Wireshark capture is reviewed throughout the video. 

Topic includes
  • NHRP Phase 2 - Spoke-to-Spoke Tunnel
  • NHRP Phase 3 - Route Summarization at Hub
  • NHRP Resolution Request/Reply
  • NHRP 'shortcut' and 'redirect' commands
  • Next Hop Server (NHS) maintains dynamic mappings between logical and physical endpoint addresses learnt at the time of endpoint registration
  • Next Hop Client (NHC) queries NHS for a physical IP address of the other spoke to build spoke-to-spoke tunnel
  • Registration message is sent every one-third of NHRP holdtime by default unless specified
  • NHRP Phases
    • Phase 1 – Hub-and-Spoke only
    • Phase 2 - Spoke-to-Spoke. Each spoke maintain next-hop information of the other spokes
    • Phase 3 – Spoke-to-Spoke with enhancement (Hierarchical Topology, Route Summarization)

About Author

Metha Cheiwanichakorn, CCIE#23585 (RS, Sec, SP), is a Cisco networking enthusiast with years of experience in the industry. He is currently working as a consulting engineer for a Cisco partner. As a founder of and an instructor at, Metha enjoys learning and challenges himself with new Cisco technologies.


When I try to configure the second tunnel on R3 the tunnel to R1 goes down. Any idea? Can you share your initial configuration file on these routers? This is for NHRP Phase 2 and 3.