> Source: [sk65072](https://support.checkpoint.com/results/sk/sk65072)

# sk65072 - How to disable 'fw early SIP nat' chain / SIP inspection

| Property | Value |
|----------|-------|
| Solution ID | sk65072 |
| Date Created | 2011-08-03 |
| Last Modified | 2024-04-01 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R81.20, R81.10 (EOS), R81 (EOS) |

## Symptoms

- * Output of `fw ctl zdebug drop` shows: "`dropped by fwmultik_process_f2p_cookie_inner Reason: PSL Drop: ADVP`"
* In packet capture we see the source port with small "i" change to a random number while it is suppose to be 5060 to 5060 by default
* SIP error code 500 in packet capture Session Initiation Protocol (500) Status-Line: SIP/2.0 500 Inte Status-Code: 500 \[Resent Packet: False\]

## Cause

The source port of the SIP protocol passing through the checkpoint is automatically changed.

## Solution

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

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