Re: cable modem reset

From: aq (njl_at_localhost.localdomain)
Date: 01/14/05


Date: Fri, 14 Jan 2005 01:52:41 GMT

On Wed, 12 Jan 2005 20:44:05 -0800, prg wrote:

> aq wrote:
<snip>
>> when i enable the network interface in xp and subsequently reboot
> into
>> linux, the ifup script either fails or gives me a local ip address
>> (something like 192.) and my linux system can't get onto the
> internet.
>> It's pretty annoying and it happens whether i disable the network
> device
>> under windows before rebooting or not.
<snip>
> Two vital pieces of info you left out -- like what brand/model (CM/dsl)
> modem and the name of your service provider/ISP.

Well, slap my thighs! i knew there was something i forgot to include. I'm
using a motorola surfboard 5100 and the ISP is telewest blueyonder.

> Sounds like your modem is cacheing client identifiers and Windows
> usually does it differently from Linux. There are several other
> posibilities but hard to guess what without the info.

It's a weird problem, it worked fine just half an hour ago when i rebooted
into linux. This time i waited a little after disabling the interface in
xp before rebooting, which i think would be consistent with allowing the
cache to empty before the reboot-am i right?
 
> You can use ethereal to inspect the dhcp packets being passed in a lease
> request by running it, then requesting a new lease. Obviously you can't
> use it at boot. It runs equally well on XP as Linux and capture files
> from one work in the other.

Will do. not sure what i'll be looking for in the captured dumps though
i'll try and figure it out.
 
> In any case, there is some item that is different in the XP request from
> the Linux request, and since unplugging the modem can "work" I suspect
> the modem is cacheing this info before it is ever sent upstream. No way
> to know without spec sheets/technical manuals or sniffing the wire.
>
> You might also look here for guidance if it is a provider quirk:
> http://www.dslreports.com/
>
> Here is an explanation of client-id differences. Note that some ISPs
> will not give out a new lease when quickly changing them -- like
> re-booting. Some just give out different IPs.
> http://homepage.ntlworld.com/robin.d.h.walker/cmtips/dhcp.html#dhcpmulti

I thought the lease was for the IP?
Usually my IP doesn't change at reboot. One other thing, if the
problem is due to the different requests used then windows should have
trouble at boot time too, right? Windows has no trouble with enabling the
network interface, which suggests to me that there is a software method
for "resetting" the modem. I guess i'll find that out using ethereal.

Cheers for the info.

Kind Regards.