View Full Version : [ubuntu] DHCP Client getting invalid IP info from ISP DHCP Server

November 14th, 2009, 08:11 PM

I am not sure where this all went wrong. All was working until yesterday. Just a quick overview of my network; I have no router presently. I have no switch. I move around my cable modem to where I need the internet (PS3 or my laptop).

So I was streaming a movie from netflix on my ps3. I wanted to work on my laptop, so I yanked the modem and moved it all to the kitchen. The ubuntu box gets an ip and all the rest of the info from the dhcp server. I can ping my own address given, but I cannot ping my default gateway. So I fight with this for a while and decide to see if the same thing happens on my XP dual boot. When it asks the dhcp server, it gets a total different address in a different subnet and everything.

I tried using dhclient3 directly and I still get the other ip info that does not work. Is there a way to force dhclient or NM to forget what address it last got? I think this is where the problem lies. The dhcp client is requesting the old address and the server is obliging...

If you need any info, just ask.



November 15th, 2009, 01:06 AM
You can see if this (http://ubuntuforums.org/showpost.php?p=7963396&postcount=2) one helps...

November 16th, 2009, 03:14 AM
Well I was able to release the IP. But when I asked for another one, it keeps giving me that one. The odd thing is, I boot up rescuecd (a linux livecd) and it gets the same ip. And it doesn't work. Windows gets a total different ip/subnet.... I am totally at a loss.....

Why would one OS get a certain IP/subnet and another get something different? Windows and PS3 work, any linux distro does not....


November 16th, 2009, 03:17 AM
Some ISPs filter connections by MAC address to prevent multiple devices from connecting to their network.

November 17th, 2009, 01:26 AM
An inexpensive router might go a long way toward solving the problem (if ISP will allow it to connect)... and save wear/tear on the connector.

November 17th, 2009, 01:31 AM
not sure if you haven't tried it, but cablemodems usually don't like being hotswapped. have you tried unplugging it for 10 minutes? I know, it sounds hoakey, but it often works.