231871452302312151452302328714523023221514523023387145230233215145230234871452302342151452302358714523023521514523023687145230236215145230237871452302372151452302388714523023821514523023987145230239215145230加上224215145230刚好32个。
计算剩于其它的可用组播IP方法：刚第三位大于128时，要减去128当第三位小于128时，要加上128这样从224－239每一组里有两个地址，刚好32个。
fr