manually forcing a IP renewal

[Owen Townend]

On Mon, 2007-11-26 at 16:28 -0500, Brian McKee wrote:
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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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Hey,
  Further to this, it is possible to give IPs based on hostname, one of
my older ISPs insisted on a random looking alphanumeric hostname they'd
given me and without it I wouldn't be able to connect. If this is a
possibility it's easy enough to put the line in dhclient.conf
  Just another idea.

cheers,
Owen.