topic Re: VPN Tunnel Flapping in General Topics

VPN Tunnel Flapping

AitorGD — Tue, 17 Oct 2017 14:34:21 GMT

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?

Regards,

Aitor

Re: VPN Tunnel Flapping

Jafar_Hussain — Sat, 27 Jun 2020 07:21:34 GMT

@AitorGD

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

Re: VPN Tunnel Flapping

MP18 — Sun, 28 Jun 2020 22:59:36 GMT

@AitorGD

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 ?

Re: VPN Tunnel Flapping

AnandNandan — Sun, 26 Jan 2025 11:16:44 GMT

Hello @MP18

I'm also facing the same issue. I'm facing this with IPsec tunnels configured in Palo Alto VM firewalls hosted in Azure VM. I try to disable DPD, but the tunnels are still flapping. The only similarity I see between the flapping tunnels and non-flapping tunnels is that the flapping tunnels are configured with tunnel monitoring towards a public IP at the peer end.

Any help is really appreciated on this troubleshooting.

Regards,

Anand