Strange portrequest while trying to open FTP sessions

[Michael Abrahamsson <michael@comitment.se>]

Hi,

I got this problem that I might need some help to solve.
I'm currently using a linux machine with ipchains as firewall and got
3 (three) different nets.

Net1: Outside the firewall
Net2: DeMilitarized Zone (Mailservers, WebServers)
Net3: Internal network

I've just opened some ports from/to the internal net (among those are
21/ftp)
but when I'm on a webpage and click a ftp link like this one:
ftp://ftp.pc.ibm.com/pub/pccbbs/pc_servers/m525w32e.txt
nothing happens and it do time out.
When I check the kernel log I can see that the workstation tried to connect 
to 204.146.167.81:18235 <-- Why the hell port 18235 (the port are differnt
from time to time..)

It works with ftp://ftp.sunet.se etc but shouldn't ftp:// always connect to 
the same port and is there a solution?

Regards,
Michael Abrahamsson