DHCP trouble with cable modem

Bill Davidsen davidsen at tmr.com
Sat Feb 16 18:57:18 UTC 2008

Bryan A. Zimmer wrote:
> Hello, friends.
> I am not new to networking and configuring desktop PC's in Fedora and
> W*ndows, but I have a problem that is at least in part due to
> unfamiliarity with DHCP.
> Here's the problem: I have a friend who also uses Comcast broadband
> cable internet. He uses Fedora almost exclusively, unless he can't
> connect to the internet, in which case he switches to W*ndows XP.. (It's
> as dual boot desktop).
> In W*ndows, he never has problem receiving an IP address from the DHCP
> server. He just configures the interface to use DHCP and, bingo! All the
> network configuration info he needs is passed right to his8k machine.
> In Fedora (both versions 7 and 8), he has chronic trouble getting
> connected to the internet. At boot time, the attempt to start up the
> interface "eth0" by requesting an IP from the DHCP server seems to fail
> about 80% of the time, even more lately. Yet I see no obvious hardware
> glitches, and the software configuration is vanilla-out-of-the-box.
I suspect this happens after he has run Windows and then runs Fedora, 
and that the modem can tell the difference between the connections. 
Therefore several ideas to try.

First, he may be able to reset the MAC address on the NIC, which will 
make the connection look like another computer. I believe Comcast allow 
up to three computers, so this may work.

Second, when shutting down a Windows boot, explicitly release the lease. 
I have no idea how to do this under Windows, I don't use it anymore. But 
I have had to release the lease to get a new connect in other cases, so 
it's worth trying. If it works it can go in a shutdown script or similar.

Bill Davidsen <davidsen at tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot

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