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When the IP system was created the designers recognized three classes of networks and thus declaired it a classful system. It was not necessary to send the subnet mask along with the IP address. The routing protocol considered the first octet, determining the class and assuming the mask. This allowed for 4,294,967,296 possible IP addresses divided into five classes. The modern classless system makes no such assumptions about the subnet mask. With classless routing the additional information, including the subnet mask, is passed along with the IP address....