You can generate 4 random numbers and store them in variables then combine them and store them in a string.
Random_IP = <Random nr 1> & "." & <Random nr 2> & "." & <Random nr 3> & "."& <Random nr 4>
You can then use tokenat(Text, index, Seperator) if you ever have to extract the numbers again.
Tokenat (Random_IP, 0, ".") <---- Will get you <Random nr 1> in above. So you simply increase the index number to get the rest of the numbers.