how respond only to specific clients

[Douglas Sterner]

Trying to use the dhcp-client-identifier option to only give out IP's to 
authorized workstations. Well the short story is it doesn't work. My 
clients all have Internal as there DCI but are unable to get an address 
with this config. Do I need to use pools, the man pages have been vague on 
examples. In addition dhcp-client-identifier, 0, 3 where can I find out 
what the 0 and 3 mean, I haven't found a good reference as of yet.
#192.168.40.X Network
class "Internal" {
  match if substring (option dhcp-client-identifier, 0, 3) = "Internal";
}
subnet 192.168.40.0 netmask 255.255.254.0 {
        pool {
                option netbios-node-type 8;
                ddns-updates on;
                range 192.168.41.120 192.168.41.245;
                option subnet-mask 255.255.254.0;
                option routers 192.168.40.1; 
                allow members of "Internal";
              deny unknown-clients;
              authoritative;
        }



Thanks 

Douglas Sterner