IP

Background and History of Subnet Masks Subnet masks were formally introduced to the TCP/IP protocol stack in RFC 950 in 1985 to address the inefficiency of the early internet’s classful addressing system. In the early 1980s, the internet relied on Class A, B, and C networks. Class A used first-octet values from 1 to 126 and supported roughly 16 million hosts, Class B used 128 to 191 and supported about 65,000 hosts, and Class C used 192 to 223 and supported 254 hosts. ...

Background and History of CIDR CIDR (Classless Inter-Domain Routing) was introduced by the IETF in 1993 through RFC 1517, RFC 1518, and RFC 1519. It later became the internet routing standard with the publication of RFC 2050 in 1998. It was created to address two major problems in the older class-based IP allocation model. First, Class C networks with 254 hosts were often too small, while Class B networks with 65,534 hosts were far too large, which led to heavy address waste. Second, internet routing tables were growing rapidly and putting pressure on router memory and processing capacity. ...

What is Classful Addressing Classful Addressing is an IP address allocation method officially introduced in 1981 through the IETF’s RFC 791 document alongside the IPv4 protocol. It was designed to efficiently distribute address space and keep routing tables small on the early Internet. The system divides addresses into 5 classes (A, B, C, D, E) based on the bit pattern of the first octet (8 bits) of the IP address, providing different sizes of network address space for each class. ...