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PC gets an Auto IP from the internet not from the DHCP on my router

Last response: in Networking
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April 21, 2011 7:01:21 AM

I am trying to sort out an IP problem on my mates PC. I have setup a Linksys wireless router on his home broadband and it works fine with my laptop and gives me a DHCP address. When I try to connect his home PC either with a wireless dongle or ethernet connect it gets a Public IP address through the router and not one of the DHCP addresses. Even if you give it a static IP address and setup the router to accept it when you turn the PC on it still gets this public IP address. It is associating with the wireless router but only gives a local connection. I have done the ipconfig and it just renews the public IP address to a different one.

There may be something on the PC doing this but I cant see any specific software that would cause this.

Can anyone help on this matter
April 22, 2011 12:20:04 AM

It's not possible. Not if you’re using a NAT router (w/ NAT enabled, of course) w/ the modem connected to the ISP over its WAN port, and your computers connected to its switch. A local DHCP request can't traverse the WAN port to get a public IP even if it wanted to, not unless there’s just a bug in the firmware.

Is this cable or dsl? If dsl, is this a single/combo modem+router, or are they separate devices?

I suggest posting the results of "ipconfig /all" from each of your computers so we can compare. Something just doesn't add up here.
April 23, 2011 6:02:25 AM

My guess is he's getting the 169.254.x.x auto config address. Which means that machine, for whatever reason, isn't able to communicate with the DHCP server.
April 25, 2011 3:28:02 PM

Are you getting an "Auto IP" or a "Public IP"? You have a couple of conflicts in your post.

As mitchflossin above said, if you are getting a 169 address it means you are not getting DHPC connection at all. A Public IP would be something that is NOT 169, 10 or 192. If you see a 70.6.78.90 or something as the IP, that is gotten from your ISP.

If you are connecting his PC to the router, maybe try a different port, or cable, or re-install the network card drivers. Last step would be to replace the network card.
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