IPv4 addresses are divided into classes. Below is the class range of IP addresses and default subnet masks:-
Class Range Default Subnet Mask
A 220.127.116.11 – 127.255.255.255 255.0.0.0
B 18.104.22.168 – 22.214.171.124 255.255.0.0
C 192.0.0.0 – 126.96.36.199 255.255.255.0
A network mask enables you to identify the network portion of an IP Address and the potion that represent the node (host). Class A, B, and C networks have default network masks, also known as natural masks, as shown here:
Class A: 255.0.0.0 (decimal)
Class B: 255.255.0.0 (Decimal)
Class C: 255.255.255.0 (decimal)
255.0.0.0 (24 bits)
In a Class A address, the first octet is the network portion while the remaining three octets are for the network manager to divide into subnets and node (hosts). Class A addresses are used for networks that have more than 65,536 hosts (actually, up to 16777214 hosts!).
255.255.0.0 (16 bits)
In a Class B address, the first two octets is the network portion while the remaining two octets are for the network manager to divide into subnets and nodes (hosts). Class B addresses are used for networks that have between 256 and 65534 hosts.
255.255.255.0 (8 bits)
In a Class C address, the first three octets is the network portion while the remaining octet is for local subnets and hosts
– perfect for networks with less than 254 hosts.