Dynamic Multipoint VPN (DMVPN) Configuration

Hi Samantha,

For some reason your OSPF hello packets don’t make it anymore to the other side, that’s what causes the dead timer to expire.

Do you have your configs? If so, mail them to me and I’ll take a look…see what’s wrong.


I wiped all the configs and started over… I swapped the 2900 out to a spoke and moved a 2811 to the hub. It ran stable for a while, even after adding ospf, but then when I started adding new ip addresses to R3 ( 2900) and it started over again with the same ‘Dead timer expired’ and “EXSTART to down, Neighbor down, Tunnel down, too many retransmissions, ignore timer exired” I then rebooted the routers. It seems to have settled, but I had to leave the lab. I’m not sure if the new 2900 router is the problem or ospf is just unstable?

Hi Samantha,

I sent you an e-mail not sure if you read it…I loaded your configs and had the same issue, after fixing a multicast mapping on the spoke router the issue was resolved.

If you want I can send you a working config.


Oh, wow, sending the working config would be terrific!! Thank you so much for you time and help with this problem!!


I went to the lab and made the changes. Everything is running stable and the network is fully connected!! Thank you so much for this DMVPN example lab and your help.

Hi Samantha,

That is great to hear! You are welcome…


Is this considered DMVPN Phase 2, and then there is just one other command on the hub to make it Phase 3?

Hi Jeffrey,

DMVPN Phase 1 and 2 are easy to understand:

- Phase 1 is a hub/spoke topology where we use mGRE on the Hub and P2P GRE on the spokes.
- Phase 2 is a hub/spoke topology where we use mGRE on the Hub and spokes.

Phase 3 takes some more then just this comment to explain. Some changes have been made to NHRP to make it more efficient. This is something I’ll cover in a future lesson.


Hi Rene
what will be the switch configuration ???

Hi Muhammed,

Not much, I just used it to connect the three routers to the same subnet. It’s just one VLAN with three interfaces in it…that’s it.


Rene i have a question, why you didnt put the Tunnel key command on routers?

awesome lesson btw.

Hi John,

With a single tunnel like in this example, there’s no need to add one.


It would be nice if we could create a separate OSPF area for each spoke but then you have to reconfigure the hub and create a tunnel interface for each of the corresponding ospf areas. For example, hub tun1 -------spoke (area1), hub tun2 ----- spoke (area2), etc. This is just in case we are expecting that the OSPF backbone area is going to grow up very quickly. In summary, this will allow reducing the hello messages traffic but then we need to give up on the mGRE/ it will turn into point-to-multipoint GRE tunnel…


Based on these configs how can we tell when we are running DMVPN phase 1, phase 2, or phase 3?

Thank you


Hi Victor,

Next week I’m going to rewrite some DMVPN posts where I will create different examples for phase 1, 2 and 3. Right now it’s a bit vague and this example isn’t enough.