DMVPN Basics part-2


sir, if i configured the source and the destination public ip addresses :-

R1 is the Next-hop-client(NHC)
R1 ) # interface tunnel 17
source fa0/0

why do i need this command :-

ip nhrp nhs (private ip address for the tunnel on the nhrp server)if we configured the source and the destination ip address of the next endpoint of the gre tunnel on R1 ? that command is useless because the gre tunnel is already have 2 endpoints only which is one endpoint is NHC and the other HAS to be the NHS

Because NHRP is NOT GRE. DMVPN is basically a technology that relies on 4 different protocols to function.

  • Multipoint GRE Tunnels
  • NHRP
  • A Routing Protocol
  • IPSec

ip nhrp nhs tells your system the tunnel ip of the NHRP NHS and what the public IP is. This maps your address to the NHRP server. Take a look at the HUB configuration, rather than the SPOKE. You’ll notice, there is no destination IP address in place. That’s because we don’t want to have to manually specify all of the spokes on the HUB. So, we use NHRP to dynamically map destinations. This also allows us to use DMVPN Phase-2 and Phase-3, which can build tunnels dynamically between endpoints.

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