Exactly what do you mean?
If you are asking about an IP address for the internet the answer is the following, whenever you connect your ISP gives you an IP that you use to communicate, this IP remains yours as long as you're connected. You have the option to havwe a static IP which means that the ISP will sell an IP address to you that will be used only by you. Hope i helped
If of course, the system you are talking about isn't going onto the internet. Then, yes, you can have your own. Just be aware that should your system connect to the internet later. You may have problems!
What Rockape is saying is that you should be careful to which interface you give an IP. If the interface you gave an IP will later on connect to the internet and you don't have a static IP then there would be a problem. Hope I helped