Subject: PORT Connection refused

From: Brian Leighfield <[email-masked]>
Date: Tue, 14 Jul 1998 06:07:00 -0400

The BLCMP FTP server is behind a firewall:- The clients are all coming in throu=
ghthe firewall.

A client will see the server as 194.80.17.40, whereas the server only
knows its self as 172.16.0.40.  Reading between your  lines this sounds
like
wu-ftp will not like this when asked to do a PORT command.

BTW are there any guidlines available for operating behind a firewall !

Brian
ps. could you please email me as [email-masked] ( not at
work )

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From: Gregory A Lundberg <[email-masked]>
Date: Tue, 14 Jul 1998 10:01:07 -0400 (EDT)

On Tue, 14 Jul 1998, Brian Leighfield wrote:

> The BLCMP FTP server is behind a firewall.  The clients are all coming
> in through the firewall.
> 
> like wu-ftp will not like this when asked to do a PORT command. 

You are correct _if_ the firewall is actually a proxy.  Proxies usually
handle connections just fine, but unless the proxy parses the control
stream (most don't) the PORT command will be passed though unchanged.  The
daemon then sees the control connection as coming from the proxy but the
PORT specifying some other IP address.

> BTW are there any guidelines available for operating behind a firewall? 

I'd take a look at moving the FTP daemon to a bastion host outside the
firewall or using some form of IP renumbering instead of a proxy to allow
access to the FTP site.

----

Gregory A Lundberg		Senior Partner, VRnet Company
1441 Elmdale Drive              [email-masked]
Kettering, OH 45409-1615 USA    1-800-809-2195