Re: PcTech Digest, Vol 5, Issue 205

[Ken Sims <mdrg6315@xxxxxxxxxxx>]

Hi Jon -

On Wed, 17 Oct 2007 13:36:07 -0400, Jon Paris
<Jon.Paris@xxxxxxxxxxxxxx> wrote:

> I thought I'd eliminated that as a possibility Scott.
>
> A) I cannot FTP to System A.
>
> B) I can FTP to System B with no problem - so apparently no firewall  
> issue on the the PC side.
>
> C) When I connect via a 5250 session to System B I can then FTP from  
> it to System A with no problem.  Those systems are in completely  
> different locations.
>
> What kind of firewall setup would exhibit this behavior?

Any decent firewall can apply a block only to certain IP address(es)
as well to only certain port(s).

System A (or some intervening firewall) could be blocking FTP
connections from the netblock that you are in, but not the netblock
that the System B is in.

I do a lot of that in my router/firewall here, blocking email
connections from residential netspace that should be relaying their
email through the ISP's mail servers, yet not blocking the ISP's mail
servers.

In the above paragraph, if you change email to FTP, residential
netspace to you, my mail server to System A, and the ISP's mail server
to System B, that gives what you are experiencing.

Ken
http://www.kensims.net/
Opinions expressed are my own and do not necessarily represent the views 
of my employer or anyone in their right mind.