DMVPN Basics


sir, what is the difference between:-

ip nhrp map multicast (public ip address)


ip nhrp map (private ip address)(public ip address) ?
also, what is this command is used for
ip nhrp nhs (private ip address for the tunnel on the nhrp server)

Hey Major,

The first command maps Multicast packets to a destination. The second command maps specific tunnel addresses to destinations.

The ip nhrp nhs tells the NHRP process the IP address of the NHS. NHRP is the “magic” of DMVPN. Think of it like this, I have a hub and spoke setup, but I want to send packets directly between two spokes. I can manually configure a tunnel between the two but that’s what we’re trying to avoid, as we might have 100 different sites. So, instead we tell NHRP a server address, and it sends a packet with it’s NBMA address and the tunnel address. Now, the NHRP Server keeps a database with that information dynamically learned. It can send a packet to both spokes telling them the addresses so they can build tunnels to each other directly, without the manual configuration.

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