DMVPN Phase 1 Connectivity

[NBenat]

Hello Team,

I have a single hub, two spokes DMVPN Phase 1 topology but I can't get connectivity between the spokes. Any help is appreciated. Thank you in advance. The attached file shows with the spokes routing tables that they can't reach each other but the tunnels between the spokes and the hub are up and running; at least from I can see. The configs are also in the attached file.

[balaji.bandi]

Not sure how is your SP config looks like, is the only have a routing issue? or anything else ?

check below exact my lab looks the same :  (hope that help to fix the issue)

https://www.balajibandi.com/?p=1750

[NBenat]

Hello Balaji.Bandi,
Thank you for your question. I enabled OSPF on all interfaces of SP
network 0.0.0.0 255.255.255.255 area 0.

[NBenat]

Hi,

I compared your and my configurations. Unfortunately, I can't see anything obvious that could explain why I can't get spoke-to-spoke connectivity. Attached is  the full lab config including SP. Thank you.

[MHM Cisco World]

 Becuase phaseI dmvpn only supports hub-spoke 

For spoke-spoke you need phaseII or phaseIII

[NBenat]

Hello MHM,
Thank you for your reply
My understanding is that Phase 1 allows Spoke-to-Spoke connectivity
through the hub. Please feel free to correct me if I'm wrong.

[MHM Cisco World]

ok, 
you mention OSPF and I see EIGRP in your config, can you more elaborate ?

[NBenat]

Hi MHM,

Sorry for the confusion. EIGRP is for the tunnel and LANs and OSPF is for
SP.

[MHM Cisco World]

show ip route in hub and spoke 
please share here

[NBenat]

here are the show ip route outputs you requested.

R11 Hub Routing Table

R31 Spoke Routing Table

R41 Spoke Routing Table

[MHM Cisco World]

no ip split-horizon eigrp 100

 replace eigrp 100 with eigrp GRE-OVERLAY in above command 

[NBenat]

I tried it but it wouldn't take it; it wants the AS number as shown below. Thank you for trying though and I do appreciate the support. I really would like to know what the problem is.

[MHM Cisco World · Accepted solution]

then only use eigrp number not eigrp named and check.

 router eigrp GRE-OVERLAY
       !
       address-family ipv4 unicast autonomous-system 100
        !
        topology base
        exit-af-topology
        network 10.1.1.0 0.0.0.255
        network 192.168.100.0
       exit-address-family

be 

 router eigrp 100
network 10.1.1.0 0.0.0.255
network 192.168.100.0
exit-address-family

[NBenat]

To be honest, I was reluctant to do it because it did take the "no split horizon" and the command was saved in the running config for the tunnel interface on the hub.

So, I replaced the EIGRP named configuration with the classic one as per your recommendation. I did it on all three routers. And it worked! I still don't understand why it fixes the problem, but at least it does. Thank you again,. If you have any idea why named EIGRP could be a problem, please share it. The screenshots below show that it is working and that the spokes can reach each other through the hub.

R31 Routing Table

R41 Routing Table

Spoke-Spoke (PC31 to PC 41)

Spoke-Spoke (PC41 to PC 31)

[MHM Cisco World]

I see in each Spoke the Hub LAN subnet but not see other Spoke LAN subnet so split-horizon is issue here not eigrp nor the DMVPN, that what I think.