Dynamic ip without DHCP client

Hi guys,im posting this thread for educational purposes. im a complete beginner to networking and to the best of my knowledge DHCP client helps you obtain an ip. I have a dynamic ip and my isp doesnt provide users with static ips either. So i wanted to experiment DHCP client service and i disabled it.

I checked comodo’s active connections to make sure no connection was being made and yes, it was completely disabled and was no longer trying to obtain an ip. Usually it would appear for a brief period of time after dialing and then disappear. But this time nothing was there.

But then i attempted to dial up my connection, i thought i wouldnt be able to connect with DHCP being disabled but i was. Then i checked my ip, disconnected and dialed again. And the ip was different than it was the first time. I redialed several times and the ip kept changing.

So my question is, how could i obtain an ip when i had DHCP disabled and didnt enter a static IP manually. And how could the ip keep updating itself? Was my network using some sort of DHCP cache function ?

Thank you

A couple of things.

  1. Which version of Windows are you using?
  2. Did you stop the DHCP Client service after you disabled it?
  3. Is your Internet connection direct or via a router/modem?
  4. What’s the IP address you get after you disable the client service?

DHCP has nothing to do with obtaining public IPs (Edit: If you use a router). The public IP is given by your provider. If you have a non-static public IP, each time when you connect your (Edit/…) router to the internet, it gets a new public IP for the while.

How do you think the PC asks for an IP address if not using DHCP?

1.xp sp2
3.Its a broadband dongle
4. a.b.c.d a and b values stay the same, c and d keep changing

Out of interest, do a and b equate to 169.254? Other than that, what kind of dongle are you using? Also, do you have any software from your ISP installed that may be used in making a connection?

If the PC would request with DHCP a public IP, and the router the like, how could i get a public IP as i have disabled DHCP in the router, and my PC just knows the IP which connects it to the router?

I think, the router is asking for a public IP adress. If DHCP is enabled or not. You even can disable the computer, and the DHCP in the router, still, the router gets an public IP at start.

Anyway, maybe it is that i spoke about the DHCP function of the router.
I am aware, if i would connect my computer to a modem with the actual setting, i would not get a connection to the internet, because my PC just knows a non-routeable IP of the router.

Edited my initial post to exclude modem connection.

No that is not the ip. Its an USB modem. It does have an application and it is set to “dynamic ip”, but does it matter because in my active connections i can not see DHCP making any sort of connection. Its disabled.

Im not following you sir, are you saying that a modem doesnt require windows based services to acquire an IP address?

I guess it depends what the application is doing. If you’ve disabled the DHCP client and you’re still getting a valid IP address, it has be be coming from somewhere. May I also assume you’re getting valid DNS server configuration as well as a valid IP address? Perhaps you could provide a little more detail about the modem/application.

I dont speak about a modem, but router. If you disable its DHCP, while your computer just knows the IP to connect to the router, the router still gets a public IP.

And for definition: If requesting of an IP address would require windows based services, all other OS would be out of luck :wink: … as the router would be, as its using linux base.

I am sure, Radaghast is more of help in this case. I just gave an experience description. May have been unrelated to the actual problem. Because you seem to speak about a modem.