option routers 192.168.100.1;
option subnet-mask 255.255.255.0;
<snip>
subnet 192.168.100.0 netmask 255.255.255.0 {
  option broadcast-address 192.168.100.255;
  allow boottp;
  allow booting;
  range dynamic-boottp 192.168.100.10 192.168.100.128;
  next-server 192.168.100.1;
  <snip>
}