System is: ubuntu 10.4. I switch manually - using the command line - from dynamic (dhcp) IP to static (fixed) IP. The steps I follow are: 1. modify the /etc/network/interfaces in order to configure eth0 as static. 2. run /etc/init.d/networking restart. Everything works fine and my eth0 has now the new, static IP. The problem is this manipulation leaves the dhclient active and running. After a while it renews the lease and my IP becomes again a dynamic one. I don't know how to stop and disable manually the dhclient. The solution I found on Ubuntu groups is to uninstall the dhclient - which is too extreme. Should be a way just to disable it. Proof is if I use the Gnome interface to do the same thing the dhclient gets stopped and disabled when the eth0 is set to static IP. Thanks for the help.