manually forcing a IP renewal

[Brian McKee]

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On 26-Nov-07, at 4:06 PM, Derek Broughton wrote:

> Brian McKee wrote:
>>> When he removes this ubuntu computer and connect his Windows  
>>> computer,
>>> the windows computers gets a ip right away.
>>
>> I believe Windows does not release IP addresses  by default.
>> Try ipconfig /release on the Windows box before you shut it down,
>> then start up the Linux box and see if it gets issued something.
>
> It's worth a try, but I don't believe it can make a difference.  As  
> far as
> the DHCP server is concerned, your computer has no OS.  All it sees  
> is a
> MAC address.  Since that is the same when you're running in Ubuntu or
> Windows, you should (and I always do) get the same IP address from the
> server

Well, it's been a bit since I was poking at this, so I may be  
remembering this incorrectly, but - the dhcp server in the cable  
modem only has a limited number of addresses it will assign (two for  
my local cable company) and if Windows doesn't release it's lease,  
then there aren't any more available until one times out, or the  
modem is power cycled long enough for it to erase it's existing leases.

When he says the Windows computer gets an ip right away, in fact it's  
just using the one it had when it shut down.

You are right that the modem doesn't care what's plugged into it - if  
he tried a new Windows computer it wouldn't work either.

Some cable companies preprogram an allowed MAC address into their  
modems and ask you for that address when you set up your account with  
them.  That's why a lot of home routers have a option to assign MAC  
numbers to their WAN port.   If it was something like that he could  
flop ethernet cards between the Windows box and the linux box just to  
prove it,  but that doesn't quite fit the symptoms he reports.

Hope that makes sense,

Brian
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