Noob here again: cannot start DHCPD

This is a freshly installed RHEL 6.8 with DNS and DHCP installed.

I get "failed" whenever I try to start a newly installed dhcpd. The dhcpd.conf file is as follows:

option domain-name "example.com";
option domain-name-servers "example.com";
default-lease-time 600;
max-lease-time 1800;
subnet 192.168.100.0 netmask 255.255.255.0 {
range 192.168.100.10 192.168.100.20;
options routers 192.168.100.1;
}

This is the example I got from my textbook, and I've tried removing quotes as well as adding them.

Any ideas ? thank you for your kind assistance.

I'm adding the exact steps I followed from the textbook below:

1. Start the virtual machine, and open a root shell. From the root shell, use the command yum -y install dhcp to install the DHCP server.
2. Open the file /etc/dhcp/dhcpd.conf with an editor, and give it the following contents. Make sure that the names and IP addresses used in this example match your network:
   option domain-name "example.com";
   option domain-name-servers YOUR.DNS.SERVERNAME.HERE;
   default-lease-time 600;
   max-lease-time 1800;
   subnet 192.168.100.0 netmask 255.255.255.0 {
   range 192.168.100.10 192.168.100.20;
   options routers 192.168.100.1;
   }
3. Start the DHCP server by using the command service dhcpd start, and enable it using chkconfig dhcpd on.