When the ARPANET was commissioned in 1969, no one anticipated that the Internet would explode out of the humble beginnings of this research project. Over the next decade, the number of hosts on the Internet grew exponentially, from 159,000 in October 1989 to over 72 million by the end of the millennium. As of January 2007, there were over 433 million hosts on the Internet. Without the introduction of VLSM and CIDR notation in 1993 (RFC 1519), Network Address Translation (NAT) in 1994 (RFC 1631), and private addressing in 1996 (RFC 1918), the IPv4 32-bit address space would now be exhausted | Chapter 6 VLSM and CIDR Routing Protocols and Concepts Topics Classful and Classless Addressing Classful IP Addressing Classful Routing Protocols Classless IP Addressing Classless Routing Protocols VLSM VLSM in Action VLSM and IP Addresses CIDR Route Summarization Calculating Route Summarization Classful and Classless Addressing Classful IP Addressing Classful Routing Protocols Classless IP Addressing Classless Routing Protocols Classful and Classless Routing Protocols Routing protocols: classful or classless. This is a result of the evolution from classful to classless IPv4 addressing. As networks began to use classless addressing, classless routing protocols had to be modified or developed to include the subnet mask in the routing update. Classful IP Addressing When the ARPANET was commissioned in 1969, no one anticipated that the Internet would explode out of the humble beginnings of this research project. Over the next decade, the number of hosts on the Internet grew . | Chapter 6 VLSM and CIDR Routing Protocols and Concepts Topics Classful and Classless Addressing Classful IP Addressing Classful Routing Protocols Classless IP Addressing Classless Routing Protocols VLSM VLSM in Action VLSM and IP Addresses CIDR Route Summarization Calculating Route Summarization Classful and Classless Addressing Classful IP Addressing Classful Routing Protocols Classless IP Addressing Classless Routing Protocols Classful and Classless Routing Protocols Routing protocols: classful or classless. This is a result of the evolution from classful to classless IPv4 addressing. As networks began to use classless addressing, classless routing protocols had to be modified or developed to include the subnet mask in the routing update. Classful IP Addressing When the ARPANET was commissioned in 1969, no one anticipated that the Internet would explode out of the humble beginnings of this research project. Over the next decade, the number of hosts on the Internet grew exponentially, from 159,000 in October 1989 to over 72 million by the end of the millennium. As of January 2007, there were over 433 million hosts on the Internet. Without the introduction of VLSM and CIDR notation in 1993 (RFC 1519), Network Address Translation (NAT) in 1994 (RFC 1631), and private addressing in 1996 (RFC 1918), the IPv4 32-bit address space would now be exhausted. High-Order Bits In the original specification of IPv4 (RFC 791), released in 1981, the authors established the classes to provide three different sizes of networks for large, medium, and small organizations. As a result, Class A, B, and C addresses were defined with a specific format for the high-order bits. IPv4 Classful Addressing Structure RFC 790 (released with RFC 791). Subnet mask for a network is determined based on its class. Only choices were networks with very large number of hosts, large number of hosts, or few number of hosts. No medium sized networks Only these three choices. 16,384 .
