"deny duplicates;" not working?

Sten Carlsen stenc at s-carlsen.dk
Tue Jan 8 20:49:06 UTC 2013

How is your configuration? do you specifically use the MAC or is it the
default (which is UID)?

On 08/01/13 20:13, Neff, Glen wrote:
> >The main piece of information to identify a client is actually the
> UID, so with a new UID -> a new client, obviously it >can not get the
> same IP, that is reserved for the old client.
> >You may have luck looking into classes and subclasses. Possibly with
> "spawn". I have never used these features >but I have a feeling they
> may actually do what you need.
> >Use the hardware = MAC to create your subclass and that could be
> independant from the UID - I think.
> Is dhcpd.conf(5) erroneous then?:
>        The duplicates keyword
>         allow duplicates;
>         deny duplicates;
>        Host declarations can match client messages based on  the 
> DHCP  Client
>        Identifier  option  or  based on the client's network hardware
> type and
>        MAC address.   If the MAC address is used, the  host 
> declaration  will
>        match  any  client  with that MAC address - even clients with
> different
>        client identifiers.   This doesn't normally  happen,  but  is 
> possible
>        when  one computer has more than one operating system installed
> on it -
>        for example, Microsoft Windows and NetBSD or Linux.
>        The duplicates flag tells the DHCP server that if a request is
> received
>        from  a  client that matches the MAC address of a host
> declaration, any
>        other leases matching that MAC  address  should  be  discarded 
> by  the
>        server,  even  if the UID is not the same.   This is a
> violation of the
>        DHCP protocol, but can prevent clients whose client
> identifiers  change
>        regularly  from  holding  many  leases  at  the same time.  By
> default,
>        duplicates are allowed.
> -G
> /*
>  * Glen R. J. Neff
>  * USD Lab Operations Infrastructure Team
>  * glen.neff at emc.com
>  *
>  * EMC^2 == E^2
>  */
> _______________________________________________
> dhcp-users mailing list
> dhcp-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users

Best regards

Sten Carlsen

No improvements come from shouting:

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