Sorry if this is a stupid question, but to get outbound active FTP connections through our firewall we need to run the following:

sudo modprobe ip_conntrack_ftp

I learned this trick from http://major.io/2007/07/01/active-ftp-connections-through-iptables/

In that article it says to persist it I should add


to /etc/sysconfig/iptables-config

But I'm not sure that is right for Ubuntu, should I add ip_conntrack_ftp to the bottom of /etc/modules instead?


2 Answers 2


Yes, you can add ip_conntrack_ftp to /etc/modules. Be attentive, you don't have to enter the modprobe command, just the name of kernel module!

  • Thanks. What do you mean? Can you just do sudo ip_conntrack_ftp insead of modprobe? Apr 14, 2014 at 12:41
  • No, add ip_conntrack_ftp line to /etc/modules.
    – Frantique
    Apr 14, 2014 at 13:04
  • 1
    Oh, I understand what you mean now. Yes, I was aware of that, but thanks for confirming. Apr 14, 2014 at 13:25

Please note that if you are using a nonstandard / custom ftp port, you can just add ports=<portnumber> to the end of the line.

For a specific example, HylaFax works using FTP protocol and begins connections using port 4559 as the control port, and then opens passive FTP ports who-knows-where. All you have to do with a custom FTP port of 4559 is sudo vi /etc/modules and then add a new line to the end of the file with ip_conntrack_ftp ports=4559.

Reboot and you should be good to go!

If you have more than one ftp service, you could also do ports=21,4559 for instance.

For this to work, you will also need the corresponding IPTABLES rules:

-A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT -A INPUT -p tcp -m tcp --dport 4559 -j ACCEPT

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