What is the difference between “classful” and “classless” IP addressing?
When the concept of IP addressing was first thought up, it was decided that IP addresses would be put into classes. These classes are: ClassIP address rangeDefault subnet mask A 1.0.0.0 to 127.255.255.255 255.0.0.0 B 128.0.0.0 to 191.255.255.255 255.255.0.0 C 192.0.0.0 to 223.255.255.255 255.255.255.0 Today, these default subnet masks aren’t much used except as a point of reference and trivia. For example, if I said that your IP address was 192.168.1.1 but didn’t tell you the subnet mask, it would be safe to assume that your subnet mask is 255.255.255.0 because that IP address falls into the Class C range. This is also important when you take some certification tests. In real life, an IP address today could have any legal subnet mask. For example, you may have an IP address of 1.1.1.1 with a subnet mask of 255.255.255.240. Or you may have an IP address of 192.192.192.192 with a subnet mask of 255.0.0.0. Sometimes, people will say things like “I need an entire Class C block of addresses
