DHCP Failover Configuration

1. Install DHCP server on nodes:

root@node1:~# apt-get install dhcp3-server
root@node2:~# apt-get install dhcp3-server

2. Important. Synchronize time on both nodes using NTP service.

3. We need to configure a config which should be identical 
   on both machines. 
   It will describe fail-over peer and range of IP addresses, 
   as well as other information as described below.
   Create it in /etc/dhcp/ and name as general or common, 
   or master. Do not forget to change dhcpd.conf include accordingly
   (see below).
 

root@node1:~# vim /etc/dhcp/dhcpd.general
root@node2:~# vim /etc/dhcp/dhcpd.general

4. Paste in each of them and change according to your needs:

ddns-update-style none;

log-facility local7;

subnet 192.168.2.0 netmask 255.255.255.0 {
  pool {
    failover peer "dhcp";
    range 192.168.1.100 192.168.1.200;
  }
  option routers 192.168.1.254;
  option subnet-mask 255.255.255.0;
# option broadcast-address 192.168.1.255;
  option domain-name "your domain";
  option domain-name-servers 192.168.1.1, 192.168.1.2;
# option ntp-servers 192.168.1.1, 192.168.1.2;
# option netbios-node-type 8;

  default-lease-time 600;
  max-lease-time 7200;

5. Configure dhcpd.conf for each node:

5.1. First node: 
   
root@node1:~# vim /etc/dhcp/dhcpd.conf
  failover peer "dhcp" {
  primary;
  address 192.168.1.1;
  port 519;
  peer address 192.168.1.2;
  peer port 520;
  max-response-delay 60;
  max-unacked-updates 10;
  mclt 600;
  split 128;
  load balance max seconds 3;
}
include "/etc/dhcp/dhcpd.general";

5.2. Second node: 
   
root@node2:~# vim /etc/dhcp/dhcpd.conf
  failover peer "dhcp" {
  primary;
  address 192.168.1.2;
  port 520;
  peer address 192.168.1.1;
  peer port 519;
  max-response-delay 60;
  max-unacked-updates 10;
  mclt 600;
  split 128;
  load balance max seconds 3;
}
include "/etc/dhcp/dhcpd.general";

6. Testing

root@node1:~# cat /var/lib/dhcp/dhcpd.leases
root@node2:~# cat /var/lib/dhcp/dhcpd.leases