> Source: [sk41431](https://support.checkpoint.com/results/sk/sk41431)

# sk41431 - The phone call from Nortel 2050 soft phone is dropped without any errors

| Property | Value |
|----------|-------|
| Solution ID | sk41431 |
| Date Created | 2009-04-19 |
| Last Modified | 2013-11-10 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |

## Symptoms

- * When a call from Nortel 2050 soft phone is passing traffic through the Firewall, it loses its connection every 2 to 5 minutes to the internal server.  

* SmartView Tracker does not show any logs about dropped traffic.  

* Kernel debug (`fw ctl debug -m fw + drop`) does not show any drops.  

* The VPN connection remains up even after the phone call is dropped.

## Cause

Nortel soft phone has a watchdog timeout of 200 seconds and the timer is reset every 100 seconds.

Nortel soft phone uses the UNISTIM protocol. Nortel soft phone would connect and then the PBX would register the phone. PBX would then send out watchdog keep-alive to the soft phone within the 200 seconds.

In this case, since connection on UDP port 5000 was idle for more than 40 seconds (default Virtual Session Timeout), Check Point FireWall-1 tears down the connection before the 200 seconds (which is normal) and treating it as a new connection.

## Solution

This solution requires authentication. Please log in to view the full solution.

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