US Region

Grandmetric LLC
Brookfield Place Office
200 Vesey Street
New York, NY 10281
EIN: 98-1615498
Phone: +1 302 691 94 10

EMEA Region

ul. Metalowa 5, 60-118 Poznań, Poland
NIP 7792433527
+48 61 271 04 43

DMVPN Phase 3 Single Hub – OSPF – Hub example

Design & Configure

DMVPN Phase 3 Single Hub – OSPF – Hub example

Traffic Flow:

  • Packet is sent from Spoke’s 1 network to Spoke’s 2 network via Hub (according to routing table)
  • Hub routes packet to Spoke2 but in parallel sends back the NHRP Redirect message to Spoke1 containing information about suboptimal path to Spoke2 and tunnel IP of Spoke2
  • Spoke1 then issues the NHRP Resolution request of Spoke’s 2 NBMA IP address to NHS with destination IP of Spoke’s 2 tunnel, this NHRP Resolution request is sent targeted to Spoke2 via NHS (according to routing table) – it is normal hop by hop NHRP forwarding process
  • Spoke2 after receiving resolution request including NBMA IP of Spoke1 sends the NHRP Resolution reply directly to Spoke1 – Reply does not traverse the Hub!
  • Spoke1 after receiving correct NBMA IP of Spoke2 rewrites the CEF entry for destination prefix – this procedure is called NHRP Shortcut
  • Spokes don’t trigger NHRP by glean adjacencies but NHRP replies updates the CEF


DMVPN Phase 3 and OSPF

  • Configure OSPF p2m type (all spokes are aware of whole topology)
  • Advertise spoke’s connected routers
  • Disable split horizon on hub (Spoke to Spoke prefix advertisement)
  • The one of OSPF limitation is single area routes summarization

DMVPN Phase 3 OSPF Hub - Spoke Example configuration


R1 – DMVPN Phase 3 – OSPF Hub configuration example:

router ospf 111
network area 0
network area 0

interface Tunnel0
ip address
no ip redirects
ip mtu 1400
ip nhrp authentication gmlabs
ip nhrp map multicast dynamic
ip nhrp network-id 111
ip nhrp shortcut
ip nhrp redirect
ip ospf network point-to-multipoint
tunnel source Loopback0
tunnel mode gre multipoint
tunnel key 123
tunnel protection ipsec profile DMVPN_PROFILE

Author: Marcin Bialy