> Source: [sk1000212](https://support.checkpoint.com/results/sk/sk1000212)

# sk1000212 - SIP over TCP Calls Fail in R82.10 When Automatic Static NAT is Used

| Property | Value |
|----------|-------|
| Solution ID | sk1000212 |
| Date Created | 2026-09-30 |
| Last Modified | 2026-10-04 |
| Technical Level | General |
| Products | Security Gateway |
| Versions | R82.10 |

## Symptoms

- * After an upgrade of the Check Point Security Gateway, SIP calls that use TCP fail to operate correctly.
* Neither side of the call receives audio.  
* Automatic Static NAT is configured for the affected deployment.
* Packet captures and debug outputs show outbound SIP payload NAT translation.
* Inbound SIP responses are not reverse-translated to the original internal address.
* The SIP 200 OK response contains the translated NAT address in the **From** field when viewed on the internal network side.

## Cause

A software condition in R82.10 can prevent the expected reverse NAT translation of inbound SIP TCP responses when Automatic Static NAT is configured. As a result, outbound SIP payload translation occurs correctly, but the corresponding inbound reverse translation is not applied.

## Solution

<br />

[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 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 Check Point Firewall / each Cluster Member / Security Group involved in the case.

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

<br />

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