Classless addressing. Types of IPv4 Addresses
Introduction Prior to 1981, IP addresses used only the first 8 bits to specify the network portion of the address In 1981, RFC 791 modified the IPv4 32-bit address to allow for three different classes Class A addresses used 8 bits for the network portion of the address, Class B used 16 bits, Class C used 24 bits. This format became known as classful IP addressing. IP address space was depleting rapidly the Internet Engineering Task Force (IETF) introduced Classless Inter-Domain Routing (CIDR) CIDR uses Variable Length Subnet Masking (VLSM) to help conserve address space. -VLSM is simply subnetting a subnet Classful and Classless IP Addressing Classful IP addressing When the ARPANET was commissioned in 1969, no one anticipated that the Internet would explode. 1989, ARPANET transformed into what we now call the Internet. As of January 2007, there are over 433 million hosts on internet Initiatives to conserve IPv4 address space include: -VLSM & CIDR notation (1993, RFC 1519) -Network Address Translation (1994, RFC 1631) -Private Addressing (1996, RFC 1918)