Dual DNS server farms in dhcpd.conf

[Glenn Satchell]

Hi John

There are three components, that when put together give this info:

1. dhcpd.conf man page
2. dhcp-options man page
3. the archives of this mailing

Not an easy combination to achieve :)

See my next reply for info about why it may/may not have worked.

regards,
-glenn

>Subject: RE: Dual DNS server farms in dhcpd.conf
>Date: Tue, 28 Apr 2009 10:11:44 -0700
>From: "John Tabasz (jtabasz)" <jtabasz at cisco.com>
>
>Hi Glenn,
>
>This is almost exactly what I was looking for. Thanks for the reply.
>I'll test it out today. 
>By the way, how would I have found this information on my own? 
>
>Thanks,
>
>John 
>
>-----Original Message-----
>From: dhcp-users-bounces at lists.isc.org
>[mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of Glenn Satchell
>Sent: Monday, April 27, 2009 9:21 PM
>To: dhcp-users at lists.isc.org
>Subject: Re: Dual DNS server farms in dhcpd.conf
>
>
>>Date: Mon, 27 Apr 2009 15:23:09 -0700
>>From: "John Tabasz (jtabasz)" <jtabasz at cisco.com>
>>
>>Hi All,
>>
>>I have a situation where I want to use dhcpd.conf to serve up addresses
>
>>that are statically assigned. I have previously used the following to 
>>do
>>this:
>>
>>shared-network TEST  {
>>
>>subnet 192.168.200.0 netmask 255.255.255.0 { option routers 
>>192.168.200.1;
>>  option subnet-mask 255.255.255.0;
>>  option domain-name-servers 10.1.1.25,10.1.2.25,10.1.3.25;
>>  option domain-name "mydomain.com";
>>deny unknown-clients;
>>}
>>
>>  host dev5c.mydomain.com                           {
>>   hardware ethernet              0:3:ba:11:b1:75;
>>   fixed-address                   192.168.200.165;
>>   option host-name                       "dev5c";
>>  }
>>
>>}
>>
>>This worked fine until a new requirement came up that the PCs on the 
>>network and the Unix workstations on the same subnet should receive a 
>>different set of DNS server IP addresses.
>>
>>I wrote a couple of perl scripts that take the host info and massage it
>
>>into the dhcpd.conf file. One way of getting what I want is to add 
>>logic into the scripts that examine the hostname and if the name 
>>indicates that the device is a PC, add the correct DNS server info into
>
>>the host declaration. This rather than using the shared-network global 
>>command to set the DNS servers for the whole subnet.
>>
>>Is there a DHCP option that returns the kernel that the client is 
>>running? If so, is there a way to use this info to manipulate the DNS 
>>entries?
>>
>>Suggestions?
>>
>
>This will identify the Windows PCs and override their dns servers. The
>subnet definition stays pretty much as it is, although you don't really
>need the shared-network around the subnet and host definitions.
>
>class "MSFT" {
>  match if substring(option vendor-class-identifier, 0, 4) = "MSFT";
>  option domain-name-servers 10.1.1.26,10.1.2.26,10.1.3.26; }
>
>regards,
>-glenn
>
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