Hope you can help. I'm using a sonicwall tz170 firewall. Here goes:
I had FTP problems with 3 customers. Basically they were unable to complete the data connection into our FTP server, the connection just locked up. I tried all sorts including opening up our firewall for high-ports, ftp ports 20 & 21 for there specific FTP public IP addresses. This still didn't resolve the issue.
I found a setting in the firewall which "Forces Inbound & Outbound FTP traffic to default to Port 20". This then resolved the above problem for these 3 customers.
However, this has had a knock on affect with a different customer, where we send the file across into there FTP site, via an automated batch file. The same is now happening here, the data connection is locking up for me. I'm fairly confident removing the setting "Forces Inbound & Outbound FTP traffic to default to Port 20" which remove this problem.
We are in the same boat as this customer, where they don't want to change things that will affect other customers, and I'm the same here. Plus from a security point of view, with all these back door threats\trojans, I'm very reluctant to continue to leave a server open for high-ports.
Does anyone have any suggestions ? I'm thinking of upgrading to the sonicOS enhanced edition, if this will give me more options with ftp ?