Can anyone explain why no firewall mods required on my dlink?

[swampy747]

uTorrent is working just fine for me, but I don't understand why. Can anyone explain the following:

I just installed utorrent and then ran the speed guide before I modified my firewall on my DLINK DI-704p. And the speed guide said the port was open and OK. I thought this really strange so I went and looked at the firewall settings. Everything is disabled, no special applications, no port forwarding, the firewall is enabled with no exceptions. So why does the port check work.

I decided to test this out. I called a friend of mine and asked him to try to telnet to my WAN ip address and the port randomly chosen by utorrent (51628). Telnet connected (this is common trick to see if a port is open, telnet doesn't do anything, it just starts if the port is open). I asked him to try another port, nope it couldn't connect. I shut uTorrent down. And now he couldn't connect. So clearly he was getting to my machine.

This made me think my firewall wasn't working at all. So I started a port listening application on another port. He couldn't connect and when I looked at my dlink log file I could see his attempt and it was blocked. Very strange I thought to myself. So I rebooted the DLINK, started my port listener on the utorrent port. My friend was blocked. I then started utorrent and ran the speed guide. Then I got him to try again. Sure enough he got in.

WHen I look at my firewall status it doesn't show any port exceptions or applications or anything. uTorrent just seems to be able to reconfigure the firewall. Now, you may be thinking ahah, its uPNP. This is a really old DLINK from around 2002, so uPNP isn't around yet.

So, I am just curious. How is utorrent working through my firewall/ reconfiguring it?

[GTHK]

NAT-PMP? ... what make and model D-Link?