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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
network 10.1.1.0 0.0.0.255
network 172.16.1.0 0.0.0.255
 
interface Tunnel0
ip address 172.16.1.1 255.255.255.0
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
end

 

 
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