> Source: [sk162012](https://support.checkpoint.com/results/sk/sk162012)

# sk162012 - After upgrading Security Gateway from R77.30 to R80.20, ftp-traffic from some Linux-FTP-clients is blocked

| Property | Value |
|----------|-------|
| Solution ID | sk162012 |
| Date Created | 2019-09-04 |
| Last Modified | 2020-11-24 |
| Technical Level | General |
| Products | Security Gateway |
| Versions | R82.10, R82, R81.20 |
| OS | Gaia |

## Symptoms

- * After upgrading Security Gateway from R77.30 to R80.20, ftp-traffic from some Linux-FTP-clients is blocked.
* Log entry may show - "Protocol violation detected with protocol:(FTP), matched protocol sig_id:(9), violation sig_id:(20)"

## Cause

According to RFC 1579, firewalls may have problems handling Active mode FTP. This is because the data connection required by FTP is opened from the server side on a previously unknown port back to the client.

## Solution

Switch to Passive mode FTP, which is recommended by RFC 1579.

"We recommend that vendors convert their FTP client programs (including FTP proxy agents such as Gopher \[3\] daemons) to use PASV instead of PORT. There is no reason not to use it even for non- firewall transfers, and adopting it as standard behavior will make the client more useful in a firewall environment."

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