Cisco Self-Study: Implementing IPv6 Networks (IPV6)

IPv4 Address Space Exhaustion

The work on IPv6 at the IETF started when a preliminary study in 1990 concluded that the IPv4 address space would be exhausted. More specifically, the IETF predicted that Class B would be exhausted within four years (1994). This study also identified the necessity to assign several adjacent Class C addresses instead of Class B addresses to organizations. Class C addresses are small, but there are plenty of them (2,097,152).

NOTE

Class C is a block that represents 255 IPv4 addresses, whereas one Class B means 65,536 IPv4 addresses. However, in reality, 253 hosts can be addressed on a Class C.

The main technical constraint of that orientation was preserving the global Internet routing table size while keeping it from ...