IPTables on FTP Server

Symptom:

You can connect to a ftp server. When you try to do anything (like ls) the client responds with no route to host or falling back to PORT instead of PASV.

Solution:

Your server is running IPTables and doesn't know how to open connections for PASV transfers.

Make sure this module is loaded:

# modprobe ip_conntrack_ftp

I load it in my iptables startup script before any rules are applied.