Why is my router allowing my NATed IP to show?

[thesun]

I have three computers, desktop1(RH8.0), desktop2(FC2), and notebook1(XP&FC2). The desktops are connected (copper cat6) to a Netgear wireless router. The notebook has no problems with a wireless connection.

I've had some other funky issues, but one that disturbs me is that when I use desktop1 (my main computer) to visit a firewall testing website, my internal NATed IP is visible to the outside world.

Why? I thought a router was supposed to mask this completely, allowing just an external IP to be visible. This issue doesn't seem to happen on desktop2 or notebook1, so I suspect some kind of configuration issue is causing the problem. Could I have set up something wrong in my desktop1 config files to cause this internal IP to show?

Thanks for any and all help. This is a major headache! :confused:

[PompeyBlue]

Is your router in DMZ mode for desktop1 ?

[taylor65]

What do you mean that your internal IP is visible? It's probably 192.168.100.something, so even if it's embedded somewhere in a packet, so what? That's an unroutable address, it means nothing.

[thesun]

Is your router in DMZ mode for desktop1 ?

No, it's not. I thought of that, but nope...not the problem. Any other thoughts?

[thesun]

What do you mean that your internal IP is visible? It's probably 192.168.100.something, so even if it's embedded somewhere in a packet, so what? That's an unroutable address, it means nothing.

Well, I'm not particularly concerned about the privacy issue, but I'm trying to figure out whether this is actually blocking anything...and as far as I'm concerned, if something is supposed to work, well, it should work.

[Jman]

Which test site did you use? I also am beheind a NAT firewall, and I've only seen my external IP appear.

[thesun]

I figured out it's related to using VNC. When I go to the site via a regular login I don't get the IP tag, but if I view it over a VNC session it can see my internal IP.

Any VNC users out there know what's going on or how to mask this?