DHCP-binding states

[crashnb]

Hello dhcp List,

i havt to write a perlscript to check how match ip-addresses are free. 
but we have a dhcp-server configurated with failover and loadbalancing. 
want to check the dhcpd.leases file for that, but i don't know what 
binding state
free(i think this lease is free), active(i think this lease is 
assigned), expired, released and backup is. can anybody describe me what 
this binding states are for.

Sorry about my bad english.

greetings

Manuel