DMVPN flapping

[Shadow7777777]

Hello,

We have some problem with one of our DMVPN config.

Our customer is reporting a problem with the DMVPN tunnel disconnecting for one of their branches. Tunnel restart on branch router may temporarily solve the problem. Deleting and re-entering the configuration on the branch router also sometimes resolves problem. However, none of the above solutions are stable and long-lasting.

Why this is happening, what we should check?

There is one log comming from IKE:

failed its sanity check or is malformed <-- can this be a couse of this? 

Whole config and some logs attached.

Many thanks for any advices or hints.

[balaji.bandi]

i am going to review the config  more detailed

High level on the Hub and Spoke, how come the IP address in the tunnel are duplicate ?

for testing Shutdown the Duplicate Tunnel interface and check the stability ?

Still issue provide what router and IOS code running ? is this issue from the Day 1 of deployment ? or been running and suddendly you see this issue ?

[Shadow7777777]

So maybe questions are, what configuration data are we missing for analysis (with what commands we can get them) except of those I attached in setup and log file? What information about the network topology we are missing? What information We are missing from the description of the problem itself?

Do we have a suspicion what could be the cause of the problem and how to fix it? Or any temporary workaround? 

I will try to collect this data and post it here to get this topic more covered.

[paul driver]

Hello
i would also check your routing, I suspect you are not creating the correct S2S peering dynamically and everything is being routed via the hubs, given that you were missing those commands on the NHS I previously mentioned 

sh ip nhrp details
traceroute xxxxx numeric

[paul driver]

Hello
I dont see your hubs setup for dynamic routing (multicast) which is required, also by default eigrp will change the next-hop address to itself when it receives then advertises prefixes towards the NHC, so this needs to negated as well.

HUBS
Int tun1
no ip next-hop-self eigrp 1
ip nhrp map multicast dynamic

[Shadow7777777]

Hello,

Just to mention solution, there was problem with IPsec, we can see in logs different spokes are connecting to HUB with the same public IP which was after some time giving link going down.

[balaji.bandi]

glad all good i was suspecting some config - but good to know you fixed the issue.