How can I configure a DHCP server to assign addresses based on the OS that is running Solved maybe!

Simon Hobson dhcp1 at
Thu Jun 3 08:57:42 UTC 2010

Marc Chamberlin wrote:

>>5.) I have been doing this a number of years. I simply assigned 
>>both interfaces the same IP, with the effect that as they use only 
>>one interface at a time, everything  worked even when switching 
>>interfaces during a download.
>>Whether this is in accordance with the RFC, I am not sure. It 
>>worked for me and was simple.
>Thanks Sten for your comments.. I would be interested in learning 
>more about your approach, but keep in mind that I am trying to 
>accomplish this task in the context of assignment of static IP 
>addresses based not only on the hardware interface addresses of 
>client machines, but on the operating system that is running on the 
>client system also...

That's the problem. I assume Sten is doing the same as I have for my laptop :

host "laptop-wired" {
   hardware ethernet aa:bb:cc:dd:ee:ff ;
   fixed address 192.168.1.n ;
host "laptop-wireless" {
   hardware ethernet uu:vv:ww:xx:yy:zz ;
   fixed address 192.168.1.n ;

This seems to work for my Mac and it's never complained when I forget 
to turn off the wireless at home. But as you have figured out, it 
won't work in a situation using classes etc since the server would 
tell you "no free leases". This is the same problem faced by people 
(such as cable internet providers) doing address assignment based on 
Option 82 - if the end user changes their equipment, then the MAC 
address no longer matches and there will be no lease free in that 
single address pool until the old lease expires (or is manually ended)

As an aside, IIRC you commented that this error message was 
misleading in an earlier message. I guess you are partially right, 
but also the error message is correct if you think of it as meaning 
"no free leases **given the constraints applied**".

Simon Hobson

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