Outbound FTP backup to Synology server from Plesk fails with CSF active

I am running an Ubuntu server with Plesk. All of these are the latest version. I am also running CSF. I am trying to FTP to my Synology server. When CSF is active, I am not able to make a connection. However, if I disable CSF, I can make the connection immediately. I have tried this on the command line interface and have been able to reproduce this.

> csf -f
> ftp 192.168.1.100 // This works
> csf -ra
> ftp 192.168.1.100 // This times out

In my csf.conf, here are the pertinent lines for the outgoing IPv4 ports

TCP_OUT = "20,21,22,25,53,80,110,113,443,587,990,993,995,5224,8443,8880,50000:65000"

I've read a little bit about this online, including resources like this. I do not think this is my problem. I am trying to have my Plesk Web server backup to my Synology NAS.

Once again, I can connect to my Synology NAS readily if CSF is stopped.

Thanks for your help with this irritating problem.

1 Answer

It dawned on me that the problem was that CSF was not allowing the FTP server to respond back. I added its IP address to the CSF - Allow file and now everything works perfectly.