DHCPD classes - How to put unknown devices in a separate class?

Randall C Grimshaw rgrimsha at syr.edu
Wed Mar 24 13:02:59 UTC 2010

With vendor class identifiers you can a.) override default configuration values such as dns servers b.) define memberships that can be used to allow access to pools.
You need to do a bit of both perhaps. Still a little vague in your description but presume you need to give private IP space to your matching devices that is defined as a secondary on the same interface. You will define a shared network with pools for each address space. The allow matching devices to use the private pool while denying matching to use the public pool. 

-----Original Message-----
From: dhcp-users-bounces+rgrimsha=syr.edu at lists.isc.org [mailto:dhcp-users-bounces+rgrimsha=syr.edu at lists.isc.org] On Behalf Of Jessica Meyer
Sent: Wednesday, March 24, 2010 3:46 AM
To: Users of ISC DHCP
Subject: Re: DHCPD classes - How to put unknown devices in a separate class?

Hi list

Thanks for your answers - Nial, Glenn and Randall.

> class "Devices_C" {
>   match if ( substring ( option vendor-class-identifier, 0, 6 ) != "vendor1"
>   and substring (option vendor-class-identifier, 0, 6 ) != "vendor2" );
>     log ( info, "Got a packet not from a vendor1 or vendor2 device" );
>     option domain-name "devicec.example.com";
> }

This does only work if the vendor-class-identifier is set, correct?
Because I cannot trust the client that it has this option set. I tried
this statement as well, then tried to add something like "or not
(option vendor-class-identifier)" but that didn't work - I'm
unfamiliar with the syntax I think.

Actually, my overall problem is: My DHCPD receives unicast DHCP
packets from one relay (say,, but I need to give out IP
addresses according to the vendor-class-identifier option. I always
failed at that. Does anyone have an example configuration or idea how
to do this? Problem is, is also a subnet, and if the
gateway is, DHCPD only gives out ip addresses from that
particular subnet.

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