Dual DNS server farms in dhcpd.conf

John Tabasz (jtabasz) jtabasz at cisco.com
Mon Apr 27 22:23:09 UTC 2009

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

shared-network TEST  {

subnet netmask {
option routers;
  option subnet-mask;
  option domain-name-servers,,;
  option domain-name "mydomain.com";
deny unknown-clients;

  host dev5c.mydomain.com                           {
   hardware ethernet              0:3:ba:11:b1:75;
   fixed-address         ;
   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




More information about the dhcp-users mailing list