VPN Tunnel Flapping

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VPN Tunnel Flapping

L1 Bithead

Hello all,


We are detecting problems with a VPN Tunnel using IKEv2. The tunnel is a L2L tunnel agains a third party vendor (Sonic Wall) the tunnel works fine on all the aspects, but sometimes the tunnel falls down and we do not why exactly. When the tunnel falls it takes onlpy a few seconds to up the tunnel again.


The error that I saw on the logs when the tunnel fall is the following:


-Event: ikev2-nego-ike-dpd-dn

-Description: IKEv2 IKE SA is down determined by DPD


It results that DPD no exists on IKEv2 and as substituction, liveness check appear, so I don't know what this error exactly is.


Can you help me?





L4 Transporter


Same issue i am facing , what was the solution you found for this.

Cyber Elite
Cyber Elite


As per logs it seems you have DPD on.

Does other side also had DPD on?

When PA sees other side Phase 1 is down then you logs showing tunnel is down.


DPD  Periodically, it will send a “ISAKMP R-U-THERE” packet to the peer, which will respond back with an “ISAKMP R-U-THERE-ACK” acknowledgement


It  might be some physical connection issue or Latency  in between  from your PA and remote end where you PA does not see 

ISAKMP R-U-THERE-ACK” acknowledgement from the other side.

Did you try to disable the DPD ?

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