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FAQ - What is the difference between the two kinds of work mode of FTP?

Publication Date:  2012-10-18 Views:  62 Downloads:  0
Issue Description
Q:
What is the difference between the two kinds of work mode of FTP?
Alarm Information
None.
Handling Process
A:
FTP has two kinds of working mode, one kind is port (active) mode, the other is passive (passive) mode. "Active" and "passive" is relative to the FTP server.
1, port (active) mode:
The client sends connection request to the server port (default is 21), the server accepts the connections, establish a control connection. When there is the need to transfer data, the client in the control connection sends PORT command to the server to tell the server it has opened the PORT and waiting for the server connection. Then the server send connection request from 20 port to client XXXX port, establish a data link to transmit data
2, passive (passive) mode:
The connection process PASV (passive) way is: the client sends connect request to the server’s FTP port (default is 21), the server accepts connections, establish a control connection. When there is the need to transfer data, server in the control connection uses PASV command told the client it has opened the XXXX port, waiting for the client connection. So the client sends the connection request to the server’s XXXX port, establish a data link to transmit data.
Root Cause
None.
Suggestions
Understand the active passive mode correctly and configure it in our company’s firewall reasonable. If the server in high priority areas, when access from the low priority area, requires open direction filtering strategy if the server works in port mode; requires open inbound direction filtering strategy if the server work in passive mode.

END