I want to make a FTP Cache with squid.

When in a host client, I put manually
IP and port squid server, I've not problems
and squid works.

How ever, when I put a iptables rule to make
FTP transparent (like http 80 port, in web case),
I can't retrieve FTP files from squid.

Somebody tell me that Squid in FTP transparnet mode
doen't work,.... is that true ? what can I do ?

Also, I've heared from Frox FTP proxy FTP server, and
that I can put work this with squid in order to get
a FTP transparent proxy with cache.

what do you say ?