Here you go, Unfortunately, in this case you can't use OBIEE Position string function as the IP has repeated number of decimals(.) in it. Only function you can use here is LOCATEN. But there is a bug in OBIEE 10g with LOCATEN syntax. So, in order to locate the 3rd '.' position, you will have to use below function:
LOCATE(expr1, expr2,int) where int is the no. you want the search to start from. For sure, in any case IPs 3rd decimal will start from position 9. So, in this case you will have to hardcode int 9 here.
So, here is your formula to be used in OBIEE:
SUBSTRING('111.222.333.444' FROM 1 FOR LOCATE('.', '111.222.333.444', 9)-1)
SUBSTRING(IP_ADD FROM 1 FOR LOCATE('.', IP_ADD, 9)-1)