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Questions about passive FTP, firewalls and Routers

 
 
Sergej Balon
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      07-12-2004, 09:20 AM
I have read some explanations about the differences of active vs. passive ftp, but there are still some
open questions:

1.) If a connection from the ftp client to the ftp server is in active or in passive mode is
a decision of the client - not of the server. Is this correct?

2.) Assume I type (as a client) at the command line:

ftp ftp.foo.com

How do I specify that I want to handle this (my ftp session) in passive mode rather than in active?

3.) Assume there is a router and a firewall at server side.
For active ftp I have to open
- Port 21 for incoming TCP request in the firewall
- Port 20 for outgoing TCP request in the firewall
- Portforwarding NAT for Port 21 to the local IP (e.g. 192.168.0.34) in the router configuration

Which settings do I have to setup for passive ftp?
As far as I know the client could initiiate the data channel to a server port from a range e.g. 1500,...,1700
Do I really have to setup NAT port forwarding for 200 ports ?

4.) Which port range is normally used for data channels ftp servers in passive mode?

5.) Assume there is a firewall at the client side.
For active ftp I (as a client) have to open
- remote Port 21 for outgoing TCP requests
- remote Port 20 for incoming TCP requests

If I use passive ftp I have to open
- all (!) remote Ports for outgoing requests because I do not know in advance which remote port range
the ftp servers offers me to communicate for the data channel. Is this correct?

6.) If you look at all ftp connections worldwide. Which percentage is handled by active ftp
and which percentage by passive ftp mode?

Thanky you for your help

Sergej
 
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