Network Foundation-- IP addressing

Classful addressing and classless addressing

Subnetting and can be changed into subnet mask (VLSM)

Subnetting: for example, class B is divided into class C, class An is divided into class B, and classful address segments are subnetted into subnets with the same mask. The address space is the same size.

Variable length subnet mask: the size of the divided address space can be different, and a network number can have a different mask. VLSM needs to run in a classless network, and the relevant protocols and software in the network need to support classless addressing.

Both subnetting and VLSM appear to make better and more efficient use of address space.

Note: the mask is used to identify the network number and host number in the IP address, 1 represents the network number, and 0 represents the host number

CIDR classless inter-domain routing: IP network number prefix is unlimited, classful addresses can be aggregated into supernets or CIDR blocks, or classful addresses can be subdivided into VLSM subnets.

Summary: classful addressing, classless addressing, subnetting, variable length subnet mask, CIDR and other technologies are all to solve the problem of efficient and flexible use of limited IPV4 32-bit address space.