It's only when you try to shoehorn old technology into the new age that you
find these esoteric problems.....

Anyway heres the thing.

I'm trying to ftp using cuteftp on win 2000 Pro behind an ADSL box to an FTP
Server (MS IIS 4.0 Version) also behind and ADSL feed.

The problem is that it can't map the correct socket and consequently wont
work.

Now before you all say use PORT mode or Use PASV. I've tried that already.
Also before you say try it on Dialup, I've tried that as well. It does work
over dialup. It works fine. But of course it doesn't run real fast ...!

After extensive reasoning I believe the problem to be that....

The NAT translator uses some header mangling to derive a random port address
that it appends to the packet header to route the packets thru from the
local lan side to the internet. Similarly on the other side the NAT pinhole
manager strips this appended header and routes to the appropriate server,
however the FTP client or server depending on whether you use PORT or PASV
embeds it's own local port address into the packet which isn't stripped or
modified by NAT in the packet and when it hits the other side it is rejected
because it doesn't include the right numbers.
The reason it works over dialup is because the dialup adapter gets routed on
the local lan thru the WAN wrapper which knows its a PPP connect rather that
an Ethernet card and therefore treats it as the gateway. Conversely when you
have a Nokia M10 the gateway is the local Lan side and therefore on the
wrong side of the NAT engine.

Catch 22. It can't possibly work without modifying either the ftp client or
server or the TCPIP stack... which seems unlikely given it aint Linux I'm
running. Or.... modifying the microcode in the Nokia...It seems that Nokia
forgot about including some kind of ftp proxy in the microcode. Bummer....

One solution could be to get hold of one of these ADSL cards that don't have
a NAT proxy in them and therefore should be treated as a PPP connected
Gateway for a mere $500.00 or so.

Another solution would be that someone here has another clever idea that I
haven't thought of.

By the way yes my pinholes are open!!!

Thanks in eager anticipation.....

greg

p.s. Greetings go out to Steve B. Haven't seen or heard from you for ages.
But it just shows that the old time soldiers never die.... By the way I
agreed with your lpd idea for remote printing, been down this one myself.
cheers.....

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Received on Thu May 4 12:10:52 2000