Nets have several properties.
These are:
'alias','nodeset' and 'initial condition'.
`Alias' means that you can assign a name to a net, for example 'IN' , 'DATA1', and so on. You have to be careful if you merge nets: when both nets have aliases or properties which are unequal '(none)', you will get a warning message. So, you should check the net properties after merging.
The alias name is used by commands which refer to nodes, for example, the noise simulation command or the optimization procedure. In both cases, one or two nets have to be defined to compute noise levels or differences between simulation results. These nets do not need to be defined via numbers because these numbers can change between subsequent netlistings ( for example, if you decide to execute the 'save cont curs' command).
'Nodeset' is the initial dc voltage to help the simulator during dcop iterations to find a correct dc operating point solution. If 'nodeset' is unequal '(none)', a '.NODESET' - SPICE3 card is added to the netlist.
'Initial condition' is used to override the dc operating point solution at the beginning of a transient simulation . Consult your SPICE3 manual. If 'initial condition' is unequal '(none)', a '.IC' - SPICE3 card is added to the netlist.