VNC server under Windows Vista - help!

[parakeet]

This is a support request on behalf of my parents, users of the
integrated Netgear DG834G modem and WiFi router combo under Windows
Vista.

We have installed for them a VNC server (UltraVNC) so that I can
connect to their desktop to provide remote support.

They have lowered their Windows Firewall, created exceptions for ports
5800 and 5900 and the application C:\Program Files\UltraVNC
\vncviewer.exe for when the firewall is active, allowed the
application through Windows Defender and set up the server to listen
on ports 5900 and 5800.

For the life of me, however, I can't manage to establish a connection
to them.

Their IP address, according to WhatsMyIP.com, is 79.75.XXX.XXX.
Hovering over the UltraVNC system tray icon, though, shows 192.168.0.3
instead. Attempts to establish a connection to either with my VNC
client fail.

I understand 192.168.0.3 to be an IP local to their network, which has
both their broadband subscription coming in to the modem and out of
the wireless cloud.

Is there any assistance you can give? I'm at the end of my tether?

 

[the wharf rat]

Is there any assistance you can give? I'm at the end of my tether?

Ummm well it sure sounds like they're behind a NAT gateway so
if that's true you'll need to establish a static mapping on the nat
side (destination nat) so that when packet arrives for 192.168.what.ever
it gets routed to the correct internal machine.

 

[parakeet]

Are we talking about port forwarding here? Or creating something with
DynDNS?

 

[the wharf rat]

Are we talking about port forwarding here? Or creating something with
DynDNS?

No I'm talking about destination nat where an external IP is
permanently mapped to an internal ip so that one or more ports on that
IP are exposed. To an external client it looks like the web server (for
instance) is running on the external ip but it's really on an internal host.

Well, I've heard it called "port forwarding" but it's really
destination nat

FWIW I seem to remember that VNC uses port 5900...

 

[parakeet]

Well I'm obviously having a hard time getting my head around this
stuff.

We had created Windows Firewall exceptions for port 5900. Also, though
my parents' broadband service is supposedly dynamic DNS, I haven't
seen it change at all from the 79.75.XXX.XXX I mentioned.

So, if it's destination NAT/port forwarding, do I need to follow the
guide at http://www.portforward.com/english/routers/port_forwarding/Netgear/DG834G/DG834Gindex.htm