How to restrict Windows XP DHCP clients to a specific subnet?

Ole Holm Nielsen Ole.H.Nielsen at
Thu Feb 13 13:30:47 UTC 2014

W.J.M. Nelis Wim.Nelis at wrote:
>> We run the ISC DCHP version 4.1.1 server that comes with Red Hat RHEL 6.5
>> Linux.  We grant DHCP leases only to known hosts, and we have files with
>> declarations of host names and their MAC addresses to achieve this.
>> We have a new challenge because we want to restrict all Windows XP PCs
>> (and we know who they are :-) to a specific VLAN subnet, where we want to
>> impose strict firewall rules.  If a user connects his XP PC to any other
>> VLAN subnet, the DHCP server must ignore this client.
>> I've searched unsuccessfully for a dhcpd.conf configuration example
>> implementing this desired goal:
>> 1. Define a subnet which *only* permits a certain list of host
>> declarations (i.e., my XP PCs) to get a lease.
>> 2. In all other subnets, the XP PCs *must not* get a lease.
> We are experimenting with an ISC DHCP configuration to achieve the goal you
> describe. Currently the following seems to do the job:
> class "Claudus" {
>          match hardware ;
>          set client-class= "Claudus" ;
> }

I have searched in vain for the "set client-class" statement.  Other 
examples of classes I've seen don't seem to use this.

Question: Is "set client-class" documented anywhere, and can I safely 
omit this?


Ole Holm Nielsen
Department of Physics, Technical University of Denmark

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