###### Unknown users network
  subnet 172.31.0.0 netmask 255.255.240.0 {
  default-lease-time 3600;
  option domain-name "isp";
  option subnet-mask 255.255.240.0;
  option domain-name-servers 172.31.0.1;
  option routers 172.31.0.1;
  range 172.31.0.100 172.31.0.254;
  }