Final answer:
Classless Inter-Domain Routing (CIDR) improves upon a Classful System by allowing for more flexible and efficient allocation of IP addresses. CIDR uses variable-length subnet masks (VLSM) to divide IP addresses into smaller, more efficient subnets. Another advantage of CIDR is more effective route summarization.
Step-by-step explanation:
Classless Inter-Domain Routing (CIDR) improves upon a Classful System by allowing for more flexible and efficient allocation of IP addresses. In a Classful System, IP addresses are divided into fixed-sized classes (Class A, B, and C) which limits the number of available addresses in each class. This often leads to inefficient use of addresses, particularly in cases where an organization needs more or fewer addresses than the class allows.
CIDR uses variable-length subnet masks (VLSM) to divide IP addresses into smaller, more efficient subnets. This means that organizations can allocate addresses based on their specific needs instead of being limited to predefined class sizes. For example, with CIDR, an organization can allocate a subnet of 1000 addresses, whereas in a Classful System, they would have been limited to a fixed number of addresses based on the class.
Another advantage of CIDR is that it allows for more effective route summarization. In a Classful System, routes are advertised based on the class, which can lead to large routing tables and increased overhead. With CIDR, routes can be summarized based on common prefixes, resulting in smaller routing tables and improved network performance.