Comment 5 for bug 247478

for dhcp you should not do anything but plug in a network cable, if you want to forcefully make the network card getting a new dhcp ip address, right click the NM applet, uncheck "enable networking", check it again and it will scan for an IP.

the manual configuration part should only be used if you actually do manual configuration of a static IP ...

roaming isnt involved in wired networking at all ...

even though teh bove mentiond actions are a bit confusing, i can confirm that dhcp doesnt get picked up as it should if i follow the documented standard way.