Dual DNS server farms in dhcpd.conf
John Tabasz (jtabasz)
jtabasz at cisco.com
Tue Apr 28 17:11:44 UTC 2009
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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