The back of the Class

Why is the IPv4 address range of not considered part of a subnet class?

A) The 127 network is used only for government and military use

B) The 127 network is not included in most TCP/IP stacks

C) The 127 network cannot be clearly delineated with binary mathematics (it’s a prime number)

D) The 127 network contains reserved addresses

E) Subnet classes are an antiquated descriptor of address segmentation

The answer: D) The 127 network contains reserved addresses

The IP address range from through is reserved for use as loopback addresses in the IPv4 TCP/IP stack. Although 127 is a prime number and the use of subnet classes is quite antiquated, neither of these reasons is why the range is usually left out of the Class A subnet.

Want to know more? Watch “Protocols and Addresses.”

The fundamental languages used over our computer networks are a standard set of protocols that are used around the world. In this video, you’ll learn about protocols and the set of standards associated with TCP/IP. You’ll also learn the essentials of TCP/IP and how subnetting can be used to build today’s modern networks.