I used to have a smoothwall between my server and the internet. Then my smoothwall had problems.
Now I have to use Suse’s built-in firewall exclusively. Who knew that you need to both allow TCP port 21 and 20! Probably most people.
Here is a good tutorial for those who are new to vsftp: http://www.ferdychristant.com/blog/articles/DOMM-6FJMR9
(Note that in addition to opening ports 21 and 20, you also have to specify FTP TCP IP in the IP Protocols field.)
