I have a machine that is connected to a network that assigns IPs automatically via DHCP, for some reason, I needed to have a static IP on that machine... I gave it an IP within the range of the DHCP... Is there's any problem in that?? Will the DHCP server consider it taken somehow automatically or I should do something manually?? And will it give that IP to other machine?? [EDIT: how can I make the DHCP server avoid using that static IP when the machine is down and not using the IP??]
Depends on the DHCP server. Some will ping IP addresses to make sure they're empty before handing them out, some will monitor ARP requests to see what's active and flag IPs as occupied if it sees traffic, some will just pass out addresses regardless of what's on 'em.
It depends on your DHCP server, really.
A better solution, if possible, is to set a DHCP reservation for that IP address. Even if the device that needs the static address can't do DCHP, the DHCP server will not pass out that address so it should be safe to use, and the MAC address in the reservation should act as documentation of a sort.