16 bits
example class b:
nnn.nnn.0.0 - nnn.nnn.255.255
subnetmask: 255.255.0.0
example class c (8 bits):
nnn.nnn.nnn.0 - nnn.nnn.nnn.255
subnetmask: 255.255.255.0
exaple class a (24 bits):
nnn.0.0.0 - nnn.255.255.255
subnetmask: 255.0.0.0
The maximum number of host bits that can be borrowed from a class A address is 22 (technically you could borrow 23 but the resulting network would be useless). A class A address uses 8 bits for its network address and 24 bits for its host addresses. Class A uses a subnet mask of 255.0.0.0 You can only borrow 22 bits (instead of 24) because a valid network requires 4 addresses: A network address, two host addresses and a broadcast address. These networks would result in 30 bits used for the network address and 2 bits used for the host addresses. These networks use a subnet mask of 255.255.255.252
Thirty bits make up the network portion of a class C address. Three bits are borrowed for the subnet mask. There is also a class A and a class B that are comprised of bits.
14
class A
ATA/ATAPI-6
The offset for a Class C IP address is 24 bits.
3 bits
The number of bits used to identify the hosts is fixed by the class of the network. Up to 24 bits can make up the host portion of a Class C address.
255.255.255.0 - in decimal representation 11111111.11111111.11111111.00000000 - binary representation (3 bytes with all the bits equal to 1, the last byte with all the bits equal to 0) /24 - binary short representation (the number of bits equal to 1)
24 bits (8 bits per octet, so 3) are used for the network portion of a class C IP address
16
Same as subnetting any other class, or a classless network. From the bits originally reserved for the host (16 bits, in the case of a class B address), you "borrow" some bits, that is, you use them to specify the subnet. The remaining bits specify an individual host within a subnet.