patching RAC with all_nodes

Hi,
When running opatch in an RAc environment, is the -all_nodes option be used by default ?

For example if we want to apply a CPU patch on all the participing RAC nodes,  running the followoing command is it enough:

opatch napply -skip_subset -skip_duplicate   

Or should we add the option -all_nodes

opatch napply -skip_subset -skip_duplicate -all_nodes

Thanks.

Kien