> Source: [sk184350](https://support.checkpoint.com/results/sk/sk184350)

# sk184350 - UDP traffic interruptions after policy installation on VSX with SecureXL UPPAK Mode 

| Property | Value |
|----------|-------|
| Solution ID | sk184350 |
| Date Created | 2025-11-20 |
| Last Modified | 2026-02-23 |
| Technical Level | General |
| Products | Security Gateway |
| Versions | R82, R81.20, R81.10 (EOS) |
| OS | Gaia |

## Symptoms

- * Voice and video calls are interrupted after policy installation. Users must leave and rejoin the calls to restore connection.
* UDP packets arrive at inbound network interfaces, but fail to forward correctly through outbound VLAN (Virtual Local Area Network) interfaces after policy installation.   
  `
  Example of packet capture using `**'cppcap'** `: `  
  `
  Outbound `**valid**` Packet:`  
  `
  16:54:30.497442 Out [`**eth2** `] 5.5.5.2:5009 > 6.6.6.2:3478 IPP 17 UDP [len 1308]`  
  `
  16:54:30.497445 Out [`**bond2** `] 5.5.5.2:5009 > 6.6.6.2:3478 IPP 17 UDP [len 1308]`  
  `
  16:54:30.497447 Out [`**bond2.400** `] 5.5.5.2:5009 > 6.6.6.2:3478 IPP 17 UDP [len 1308]`  
  `
  `  
  `

  Outbound `**invalid**` Packet:`  
  `
  16:54:30.597317 Out [`**eth2** `] 5.5.5.2:5009 > 6.6.6.2:3478 IPP 17 UDP [len 1308]`  
  `
  16:54:30.597318 Out [`**bond2** `] 5.5.5.2:5009 > 6.6.6.2:3478 IPP 17 UDP [len 1308]`  
  `
  `**Missing sending out to the vlan.**`
  `
* Switching SecureXL from UPPAK mode to KPPAK mode resolves the issue.

## Cause

When a policy is installed on a VSX gateway using SecureXL UPPAK mode, the system incorrectly handles accelerated UDP connections. Specifically:  

* Routing cache is not updated: The fast-path routing information for existing connections is not refreshed after policy installation.
* VLAN tagging errors: VLAN tags are either missing or incorrect on outbound packets.

As a result, packets traveling through the fast path (accelerated connections) are sent without proper VLAN tags or are not sent at all through the correct VLAN interfaces.  

This problem specifically affects UDP traffic because UDP connections in UPPAK mode rely on cached routing and interface information that becomes stale after policy changes.

## Solution

This problem was fixed. The fix is included starting from:

* [Jumbo Hotfix Accumulator for R81.20](https://sc1.checkpoint.com/documents/Jumbo_HFA/R81.20/Default.htm) starting from Take 120
* Jumbo Hotfix Accumulator for R82 starting from Take 60

Check Point recommends to always upgrade to the [Recommended version](https://support.checkpoint.com/results/sk/sk95746) ([Security Gateway](https://support.checkpoint.com/product/73) / [VSX](https://support.checkpoint.com/product/359) / [Security Management Server](https://support.checkpoint.com/product/184) / [Multi-Domain Security Management Server](https://support.checkpoint.com/product/166) / [SmartConsole](https://support.checkpoint.com/product/191)).

If you choose not to upgrade, [contact Check Point Support](https://www.checkpoint.com/support-services/contact-support/) to get a Hotfix for your version.

A Support Engineer will make sure the Hotfix is compatible with your environment before providing it.  
For faster resolution and verification, collect these files:

1. [CPinfo](https://support.checkpoint.com/results/sk/sk92739) file from the Management Server involved in the case.
2. [CPinfo](https://support.checkpoint.com/results/sk/sk92739) file from the Security Gateway / each Cluster Member involved in the case.

**Hotfix installation instructions:**   
Refer to [sk168597 - How to install a Hotfix](https://support.checkpoint.com/results/sk/sk168597).

---

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