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Grandmetric LLC
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ul. Metalowa 5, 60-118 Poznań, Poland
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Grandmetric LTD
Office 584b
182-184 High Street North
E6 2JA
+44 20 3321 5276

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  • DMVPN Phase 3 Single Hub – EIGRP – Hub example

    Design & Configure

    DMVPN Phase 3 Single Hub – EIGRP – 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 EIGRP

    • Advertise spoke’s connected routes
    • Disable split horizon on hub (Spoke to Spoke prefix advertisement)
    • Enable Next-hop-self feature


    DMVPN Phase 3 EIGRP Hub - Hub Example configuration


    R1 Hub configuration example:

    router eigrp 111

    interface Tunnel0
    ip address
    no ip redirects
    ip nhrp authentication gmlabs
    ip nhrp map multicast dynamic
    ip nhrp network-id 111
    ip nhrp shortcut
    ip nhrp redirect
    no ip split-horizon eigrp 111
    no ip split-horizon
    tunnel source Loopback0
    tunnel mode gre multipoint
    tunnel key 123
    tunnel protection ipsec profile DMVPN_PROFILE


    Author: Marcin Bialy