As you are performing a range query you need to have the same start and end point when you split the interval up as the end value is not included (range is[start <= value < end]). clientIP: [66.249.64.0 TO 66.249.80.0] and clientIP: [66.249.80.0 TO 66.249.94.0] would therefore cover the full range.
If you want to instead map the field as ip you will need to reindex the data into a new index with the correct mapping.