We have about 500 public IP addresses and is about to run dry. Most of the hosts are configured to get the IP from DHCP.
But there some that was configured with static IP.
Now I would like to free those IP addresses, where the host no longer exist.
For the DHCP IP's it is easy; There I can just look in the DHCP server and check when each IP was last issued. If not within X months, then I declare it as free and if the host should come online again, it will just get another IP.
But what about for those hosts that used static IP's?
I can ping the IP and if it doesn't reply then maybe is it free.
But what if I give the IP to a new host, because I think it is free, and the old host one day comes online? Problem!
How do you clean up your IP's in such a situation and prevent "ghost hosts" from coming back online and claim their IP address again?