What major issue arises from the rigid boundaries of classful addressing?

The major issue that arises from the rigid boundaries of classful addressing is the wasted IP address space. In classful addressing, networks are divided into fixed classes (Class A, B, C, etc.) based on the first few bits of the IP address. Each class corresponds to a specific range of IP addresses and supports a predetermined number of hosts.

This rigid structure means that organizations often end up with more addresses than they actually need. For example, a Class A address provides a vast number of potential hosts, typically far exceeding the requirements of smaller organizations. Consequently, many of these addresses go unused, leading to significant wastage of the available IP address space.

As the internet grew and the demand for IP addresses increased, the limitations of classful addressing became apparent, prompting the shift to Classless Inter-Domain Routing (CIDR), which allows for more flexible allocation of address space and utilizes it more efficiently. This transition was essential to accommodate the growing number of devices and networks, ensuring better utilization of available IP addresses.