> Source: [sk183300](https://support.checkpoint.com/results/sk/sk183300)

# sk183300 - VoIP SIP calls work only in one direction

| Property | Value |
|----------|-------|
| Solution ID | sk183300 |
| Date Created | 2025-04-01 |
| Last Modified | 2025-04-10 |
| Technical Level | Advanced |
| Products | Security Gateway, Scalable Platforms |
| Versions | R82, R81.20, R81.10 (EOS), R82, R81.20, R81.10 (EOS) |
| OS | Gaia |

## Symptoms

- * Voice over IP (VoIP) calls using the Session Initiation Protocol (SIP) function in only one direction.

* Security Gateway does not perform NAT to payload packets when forwarding them to the VoIP server.

* Kernel debug on the Security Gateway ("`fw ctl debug -m fw + align`") shows:

  `sip_ws_parser_header_name_cb: failed, number of headers exceeds the allowed value; the allowed value is:30 ;`  
  `
  sip_ws_parser: Parsing failed!;`

## Cause

The number of headers allowed in a single SIP message is limited for security reasons. By default, this threshold is set to 30.

The affected SIP traffic contains more headers than the configured threshold.

## Solution

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

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