The 'schema' I've followed was suggested to me from onlines tutorials. They always says: "limit the ip range assignment by the router". I've never heard about someting like 'avoid duplicate ip assignment', that would imply a previous scanning of existing acive ip on the network by the router. And assuming that this 'previous scanning' could exist, what about a static ip desktop turned on after dhcp assignment? It doesn't care if the same of his ip is already in use.

Quote Originally Posted by Harry Kuhman
...without having to move back to the Live CD systems and look up what IP...
As concern this isssue you can use 'nmap' to scan the network ips.