US Region

Grandmetric LLC
Lewes DE 19958
16192 Coastal Hwy USA
EIN: 98-1615498
+1 302 691 94 10

EMEA Region

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


Grandmetric LTD
Office 584b
182-184 High Street North
E6 2JA
+44 20 3321 5276

  • en
  • pl
  • 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