> Source: [sk110620](https://support.checkpoint.com/results/sk/sk110620)

# sk110620 - Idle connection that was accelerated by SecureXL is dropped with "First packet isn't SYN" log after it becomes active again

| Property | Value |
|----------|-------|
| Solution ID | sk110620 |
| Date Created | 2016-03-21 |
| Last Modified | 2025-01-21 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20, R81.10 (EOS), R81 (EOS) |
| OS | Gaia |

## Symptoms

- * "`First packet isn't SYN`" drop log in SmartConsole / SmartView Tracker.

* Disabling SecureXL resolves the issue (applies only to R77.30 and lower versions).

* Traffic capture, the drop log, and output of "`fwaccel conn`" command on the Security Gateway, show that the dropped connections were accelerated by SecureXL, then were idle for more that 512 seconds and then became active again.

## Cause

?By design, the SecureXL mechanism does not update the TCP expiration timeout timer in the FireWall kernel, if the connection was idle for more than 512 consecutive seconds.

## Solution

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

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