Re: nas???

[Seth R Arnold <sarnold@willamette.edu>]

On Mon, Sep 06, 1999 at 10:15:23AM -0700, Patrick Olson wrote:
> 
> On Mon, 6 Sep 1999, John Gay wrote:
> 
> > there is an easier way, but as I said, I'm new to all this. I have
> > noticed that several ftp sites won't let me connect because they can't
> > resolve my address, or something like that. Is this a problem with my
> > setup or my ISP? 
> 
> That "could not resolve" message might be a DNS problem, but I would need
> a more exact error message to know for sure.  I'm sorry, but that one just
> isn't enough data for me to figure out where the problem lies.

[extremely liberal snipping]

For the 'cannot resolve your address' error, chances are good it is a
security mechanism by the ftp server. This will take a bit of explaining,
and (as always :) I am not terribly qualified, having never written an ftp
server nor ftp client. :) Nor DNS server nor DNS resolver. :)

There are two directions DNS can go -- the most common way users see is
"www.yahoo.com" --> 204.71.200.67 conversion. The other way, known as
"reverse DNS" takes 204.71.200.67 and converts that to www.yahoo.com.

It is possible for DNS to get corrupted to the point that machines can have
www.yahoo.com resolve to some other address -- and a security test is to
check the address given by that transformation using reverse DNS and make
sure it gives the same www.yahoo.com address back.

Dialup ISPs therefore should probably put in DNS entries for each one of
their dialup lines -- including the reverse DNS, which your ISP either
doesn't have, or it is misconfigured -- or something else is broken, and I
am sputing hot air. 

:)

-- 
Seth Arnold | http://www.willamette.edu/~sarnold/
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