> Source: [sk172046](https://support.checkpoint.com/results/sk/sk172046)

# sk172046 - Occasionally, traffic stops passing over an IKEv1 Site to Site VPN tunnel between a Check Point Security Gateway and a 3rd party VPN device

| Property | Value |
|----------|-------|
| Solution ID | sk172046 |
| Date Created | 2021-02-15 |
| Last Modified | 2021-11-28 |
| Technical Level | General |
| Products | Security Gateway |
| Versions | R81.10 (EOS), R81 (EOS) |

## Symptoms

- * Occasionally, traffic stops passing over a Site to Site VPN tunnel based on IKEv1 between a Check Point Security Gateway and a 3rd party VPN device.

* Traffic passes correctly again over a Site to Site VPN tunnel after tearing down and starting the VPN tunnel.

* VPN logs do not show any traffic drops during the issue.

* This issue may only impact traffic from specific subnets while traffic from other subnets passes without an issue.

* VPN traffic monitoring shows that the traffic passes correctly again over a Site to Site VPN tunnel after the next IKE Phase2 rekeying occurs between the affected subnets.

* IKE debug on the Check Point Security Gateway shows that when it initiates the IKE Phase2 negotiation for a specific subnet, the 3rd party VPN device also initiates the IKE Phase2 negotiation for the same subnet within a fraction of a second.

## Cause

The download of the Security Association (SA) to the kernel is delayed when a Check Point Security Gateway initiates the Quick Mode (QM) renegotiation.

This delay exists to assure the VPN peer managed to save the SA. In this case, there is a possibility for a traffic outage if the VPN peer also initiates QM renegotiation in this small timeframe.

<br />

## Solution

[Contact Check Point Support](https://www.checkpoint.com/support-services/contact-support/) to get a Hotfix for this issue.   
A Support Engineer will make sure the Hotfix is compatible with your environment before providing the Hotfix.   
For faster resolution and verification please collect [CPinfo](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk92739) files from the Security Management and Security Gateways involved in the case.

**Hotfix installation instructions:**   
Refer to [sk168597 - How to install a Hotfix](https://supportcenter.checkpoint.com/supportcenter/portal?eventSubmit_doGoviewsolutiondetails=&solutionid=sk168597).

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