Basic DMVPN configuration
Hub Router config - R1
interface Tunnel0
bandwidth 1000
ip address 100.100.100.1 255.255.255.0
no ip redirects
ip mtu 1400
no ip split-horizon eigrp 100
ip nhrp map multicast dynamic
ip nhrp network-id 12345
ip nhrp holdtime 5
ip nhrp redirect
ip tcp adjust-mss 1380
delay 1000
tunnel source FastEthernet1/0
tunnel mode gre multipoint
tunnel key 12345
Spoke Router config - R5
interface Tunnel0
bandwidth 1000
ip address 100.100.100.5 255.255.255.0
no ip redirects
ip mtu 1400
ip nhrp map 100.100.100.1 17.17.17.1 <-- Maps the inside hub address to the outside hub address
ip nhrp map multicast 17.17.17.1 <-- Maps multicast packets to the outside address of the hub
ip nhrp network-id 12345
ip nhrp holdtime 5
ip nhrp nhs 100.100.100.1 <-- Specifies who is the hub of the DMVPN cloud
ip nhrp shortcut
ip tcp adjust-mss 1380
delay 1000
tunnel source FastEthernet5/0
tunnel mode gre multipoint
tunnel key 12345
Dual & Triple Hub DMVPN
If you want multiple Hubs for redundancy, configure the alternate Hubs similar to R1, and on each Spoke router, create mappings for the alternate Hub or Hubs
interface Tunnel0
ip nhrp map 100.100.100.2 27.27.27.2
ip nhrp map multicast 27.27.27.2
ip nhrp map 100.100.100.3 38.38.38.3
ip nhrp map multicast 38.38.38.3
Then list the Hub routers in priority of preference
ip nhrp nhs 100.100.100.1 priority 1
ip nhrp nhs 100.100.100.2 priority 2
ip nhrp nhs 100.100.100.3 priority 3
*Note: A Hub router can also be a "Spoke" to another Hub router. If you need to configure a Hub as a "Spoke" to the other Hubs, you would do so by using the same mapping statements and prioritization above, just like on the other Spokes, but leave in the Hub NHRP commands.
interface Tunnel0
bandwidth 1000
ip address 100.100.100.1 255.255.255.0
no ip redirects
ip mtu 1400
no ip split-horizon eigrp 100
ip nhrp map multicast dynamic
ip nhrp network-id 12345
ip nhrp holdtime 5
ip nhrp redirect
ip tcp adjust-mss 1380
delay 1000
tunnel source FastEthernet1/0
tunnel mode gre multipoint
tunnel key 12345
Spoke Router config - R5
interface Tunnel0
bandwidth 1000
ip address 100.100.100.5 255.255.255.0
no ip redirects
ip mtu 1400
ip nhrp map 100.100.100.1 17.17.17.1 <-- Maps the inside hub address to the outside hub address
ip nhrp map multicast 17.17.17.1 <-- Maps multicast packets to the outside address of the hub
ip nhrp network-id 12345
ip nhrp holdtime 5
ip nhrp nhs 100.100.100.1 <-- Specifies who is the hub of the DMVPN cloud
ip nhrp shortcut
ip tcp adjust-mss 1380
delay 1000
tunnel source FastEthernet5/0
tunnel mode gre multipoint
tunnel key 12345
Dual & Triple Hub DMVPN
If you want multiple Hubs for redundancy, configure the alternate Hubs similar to R1, and on each Spoke router, create mappings for the alternate Hub or Hubs
interface Tunnel0
ip nhrp map 100.100.100.2 27.27.27.2
ip nhrp map multicast 27.27.27.2
ip nhrp map 100.100.100.3 38.38.38.3
ip nhrp map multicast 38.38.38.3
Then list the Hub routers in priority of preference
ip nhrp nhs 100.100.100.1 priority 1
ip nhrp nhs 100.100.100.2 priority 2
ip nhrp nhs 100.100.100.3 priority 3
*Note: A Hub router can also be a "Spoke" to another Hub router. If you need to configure a Hub as a "Spoke" to the other Hubs, you would do so by using the same mapping statements and prioritization above, just like on the other Spokes, but leave in the Hub NHRP commands.