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Date:      Sun, 4 Aug 2002 22:45:27 -0400
From:      "Eric Olsen" <ericg@chartertn.net>
To:        "Kevin Oberman" <oberman@es.net>, Terry Lambert <tlambert2@mindspring.com>
Cc:        Bri <brian@ukip.com>, freebsd-stable@freebsd.org, freebsd-hackers@freebsd.org
Subject:   Re: dhcp problems with my ISP 
Message-ID:  <200208050245.g752jRl05024@kpt-c-24-158-106-133.chartertn.net>
In-Reply-To: <20020805011220.5E8875D03@ptavv.es.net>
References:  Your message of "Sat, 03 Aug 2002 03:17:17 PDT." <3D4BADAC.481BB6E3@mindspring.com> 

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On 4 Aug 2002 at 18:12, Kevin Oberman wrote:

> > Date: Sat, 03 Aug 2002 03:17:17 -0700
> > From: Terry Lambert <tlambert2@mindspring.com>
> > Sender: owner-freebsd-stable@FreeBSD.ORG
> > 
> > Bri wrote:
> > > Hi I have a Cable and have a Cable Modem for my internet connection
> > > of which you use dhcp to obtain an IP address great but this only
> > > seems to work successfully on a Windows machine I've registered all
> > > the other mac addresses of unix boxes and Apple macs I have and they
> > > seem to have alot of difficulty obtaining IP addresses. Especially
> > > the UNIX machines which run FreeBSD 4.5-RELEASE or 5.0-CURRENT on
> > > sparc64 at the moment the sparc64 box which is a Sun Ultra 5 which
> > > is the worst for detecting an IP with dhclient.
> > > 
> > > What I would really like to know is what does the windows dhcp do
> > > differently than say dhclient.
> > > 
> > > I would be very interested to know as I would like a UNIX machine
> > > that can maintain and IP address.
> > 
> > Use the same exact NIC.
> > 
> > Often, once the cable company sees a MAC address, it filters all
> > other MAC addresses from getting a lease from your wire.
> > 
> > The intent of this is to prevent people grabbing more than one
> > lease simultaneously, or running more than one machine at a time.
> > 
> > Ask Julian Elisher.  He had exactly this problem with a machine
> > in San Francisco, 2 years ago.
> > 
> > Note: If you ask, he will say "Yes, I had exactly this problem";
> > he won't tell you anything you can do about it, except "Use the
> > same exact NIC", because that's really the only fix.
> 
> I have found that the problem is fixed by re-starting the cable modem
> when a different NIC is inserted. The problem was not with DHCP, but
> with the cable modem's forwarding table.
> 
> My experience was with the old Motorola CyberSurfer modem used by
> @Home in its early days. Not sure that this applies to other or newer
> cable modems.
> 
Sometimes the only way is to have the new machine spoof the MAC address of the old 
machine's NIC.

ifconfig dc0 ether 00:01:02:03:04:05

but you gotta be careful not to end up with two machines with the same MAC address 
hanging around..

Eric


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