REal World DMVPN issue

Hello everybody,

 

I am posting this, as i have issue in the DMVPN in our network at my work.

 

the issue is that we have an HQ connected to 10 branhes using MPLS L3 as the underlay network.

 

last week we configured DMVPN as the overlay without doing any type of encryption.

 

the issue is that the HUB router keeps listing the spokes as the following output:

 

Core-Router-Branches#sho dmvopn

                            ^

% Invalid input detected at '^' marker.

 

Core-Router-Branches#sho dmvpn

Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete

        N - NATed, L - Local, X - No Socket

        # Ent --> Number of NHRP entries with same NBMA peer

        NHS Status: E --> Expecting Replies, R --> Responding

        UpDn Time --> Up or Down Time for a Tunnel

==========================================================================

 

Interface: Tunnel0, IPv4 NHRP Details

Type:Hub, NHRP Peers:6,

 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb

 ----- --------------- --------------- ----- -------- -----

     0    0.0.0.0    10.10.253.2    NHRP     xi

     0    0.0.0.0    10.10.253.3    NHRP     xi

     0    0.0.0.0    10.10.253.4    NHRP     xi

     0    0.0.0.0    10.10.253.5    NHRP     xi

     0    0.0.0.0    10.10.253.7    NHRP     xi

     0    0.0.0.0    10.10.253.10   NHRP     xi

 

The only way to fix this is to flap all the spokes tunnel interfaces. after a while the spokes gets diconnected and the above output appears again

When i dubug nhrp, the HUB seems to keep sending NHRP requests, where it only has recieve requests and send acknowlgements.

Below is the tunnel interface configuration of the HUB and one of the spokes:

 

====================================

HUB 

====================================

interface Tunnel0

 ip address 10.10.253.1 255.255.255.0

 no ip redirects

 ip mtu 1400

 ip nhrp map multicast dynamic

 ip nhrp network-id 1

 ip nhrp holdtime 65535

 tunnel source GigabitEthernet0/1

 tunnel mode gre multipoint

 tunnel key 10

 

==========================================

SPOKE

==========================================

Current configuration : 337 bytes

!

interface Tunnel0

 ip address 10.10.253.10 255.255.255.0

 no ip redirects

 ip mtu 1400

 ip nhrp map 10.10.253.1 172.16.34.2

 ip nhrp map multicast 172.16.34.2

 ip nhrp network-id 1

 ip nhrp holdtime 65535

 ip nhrp nhs 10.10.253.1

 ip tcp adjust-mss 1300

 tunnel source FastEthernet0/0/0

 tunnel mode gre multipoint

 tunnel key 10

end

 

I know that this forum is dedicated to those who are persuing CCIE , but i am one of those who are on the same persuite, and i think that DMVPN is on the outline of the exam and would like to share this strange behaviour of DMVPN as part of the preparation :)

 

Best Regards

Ibraheemo 

 

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