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Index of Chilkat Blog Posts

June 7, 2007

FTP Blockers - TCP/IP Port Filtering and Anti-Virus

Making FTP work between client and server can be quite difficult. There are often several layers of protection, any of which can block successful FTP operation.

A previous post already discussed Deep Inspection Firewalls and Passive FTP.

This post describes two additional barriers at the FTP server. The first is TCP/IP port filtering. On your FTP server, check your TCP/IP settings to make sure you’re not blocking traffic in the dynamic (ephemeral) port range used by FTP for data transfers. On Windows computers, the ephemeral port range is 1024 to 5000 (typically). To check for port filtering, examine your TCP/IP Properties. Click on "Advanced", then click the "Options" tab, then select "TCP/IP filtering" and click "Properties". Check to see if "Enable TCP/IP Filtering" is checked. If so, disable it.

The 2nd potential barrier on the FTP server is anti-virus. My server runs McAfee VirusScan Enterprise. It has Access Protection properties where it’s possible to select pre-defined port-blocking rules (typically for email, IRC, and FTP), as well as establish your own port blocking rules. Make sure you’re not blocking the FTP ports or the ephemeral port range.

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