What is IPv4 Address classes?

By | 9th November 2015

IPv4 addresses are divided into classes. Below is the class range of IP addresses and default subnet masks:-

                             Class                        Range                                           Default Subnet Mask
A                         1.0.0.0 – 127.255.255.255                       255.0.0.0
B                         128.0.0.0 – 191.255.255.255                   255.255.0.0
C                         192.0.0.0 – 223.255.255.255                  255.255.255.0

Network mask
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)

(11111111.00000000.00000000.00000000) binary

Class B:    255.255.0.0 (Decimal)

(11111111.11111111.00000000.00000000) binary

Class C:    255.255.255.0 (decimal)

(11111111.11111111.11111111.00000000) binary

Class A:

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!).

Class B
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.

Class C
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.




Subnetting IPv4 Addresses

Subnetting Class B IP Address

VLSM

CIDR




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