What are the 5 classes of IP address define each?

An IPv4 address class is a categorical division of internet protocol addresses in IPv4-based routing.

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Class A Address
Class B Address
Class C Address
Class D Address
Class E Address
What are the types of IP address classes define each?
Why are the IP addresses classified into 5 classes and how to find the class of a certain IP?
How many IP addresses are in each class?

Separate IP classes are used for different types of networks. Some are used for public internet-accessible IPs and subnets, that is, those networks behind a router (as in classes A, B and C). As well, some classes are reserved by the Internet Engineering Task Force (IETF) and the Internet Assigned Numbers Authority (IANA) for specific purposes. These special ranges are used for multicasting of identical data to all computers on a network or subnet or for research (as in classes D, E).

Within this notation, classes are mainly differentiated by the number of bits they have for the network and the number of bits used for hosts. IP addresses are notated in four groups of three-digit representations of 8 bits of binary in base 10-formatted notation for a total of 32 bits. The groups are separated by periods starting from zero (which in binary would be 00000000); the highest number in a grouping is 255 (or 11111111).

IPv4 address classes:

Class A IP addresses, where the 1st bit is 0, encompass the range of 0.0.0.0 to 127.255.255.255. This class is for large networks and has 8 bits for network and 24 bits for hosts.

Class B IP addresses, where the 1st two bits are 10, are in the range of 128.0.0.0 to 191.255.255.255. This class is for medium networks and has 16 bits for network and 16 bits for hosts.

Class C IP addresses, where the 1st three bits are 110, are in the range of 192.0.0.0 to 223.255.255.255. This class is for smaller networks and has 24 bits for network and 8 bits for hosts.

Class D or multicast IP addresses, where the 1st four bits are 1110 are in the range of 224.0.0.0 to 239.255.255.255

Class E or experimental IP addresses, where the 1st four bits are 11110, are in the range of 240.0.0.0 to 255.255.255.255.

Prior to the introduction of IPv6 as a solution to the internet’s running out of addresses, the idea of opening the class E addresses was hotly debated. While forming the basis for IP address assignment, the system of IP address classes described here is generally bypassed today by use of Classless Inter-Domain Routing (CIDR) addressing.

This was last updated in October 2020

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Internet Protocol hierarchy contains several classes of IP Addresses to be used efficiently in various situations as per the requirement of hosts per network. Broadly, the IPv4 Addressing system is divided into five classes of IP Addresses. All the five classes are identified by the first octet of IP Address.

Internet Corporation for Assigned Names and Numbers is responsible for assigning IP addresses.

The first octet referred here is the left most of all. The octets numbered as follows depicting dotted decimal notation of IP Address −

The number of networks and the number of hosts per class can be derived by this formula −

When calculating hosts' IP addresses, 2 IP addresses are decreased because they cannot be assigned to hosts, i.e. the first IP of a network is network number and the last IP is reserved for Broadcast IP.

Class A Address

The first bit of the first octet is always set to 0 (zero). Thus the first octet ranges from 1 – 127, i.e.

Class A addresses only include IP starting from 1.x.x.x to 126.x.x.x only. The IP range 127.x.x.x is reserved for loopback IP addresses.

The default subnet mask for Class A IP address is 255.0.0.0 which implies that Class A addressing can have 126 networks (27-2) and 16777214 hosts (224-2).

Class A IP address format is thus: 0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH

Class B Address

An IP address which belongs to class B has the first two bits in the first octet set to 10, i.e.

Class B IP Addresses range from 128.0.x.x to 191.255.x.x. The default subnet mask for Class B is 255.255.x.x.

Class B has 16384 (214) Network addresses and 65534 (216-2) Host addresses.

Class B IP address format is: 10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH

Class C Address

The first octet of Class C IP address has its first 3 bits set to 110, that is −

Class C IP addresses range from 192.0.0.x to 223.255.255.x. The default subnet mask for Class C is 255.255.255.x.

Class C gives 2097152 (221) Network addresses and 254 (28-2) Host addresses.

Class C IP address format is: 110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH

Class D Address

Very first four bits of the first octet in Class D IP addresses are set to 1110, giving a range of −

Class D has IP address range from 224.0.0.0 to 239.255.255.255. Class D is reserved for Multicasting. In multicasting data is not destined for a particular host, that is why there is no need to extract host address from the IP address, and Class D does not have any subnet mask.

Class E Address

This IP Class is reserved for experimental purposes only for R&D or Study. IP addresses in this class ranges from 240.0.0.0 to 255.255.255.254. Like Class D, this class too is not equipped with any subnet mask.

What are the types of IP address classes define each?

This addressing method divides the IP address into five separate classes based on four address bits. Here, classes A, B, C offers addresses for networks of three distinct network sizes. Class D is only used for multicast, and class E reserved exclusively for experimental purposes.

Why are the IP addresses classified into 5 classes and how to find the class of a certain IP?

Class numbers There were five different classes and the grouping was done based on the first few bits as per the first octet in the IP address. Of these classes, Classes A, B, and C are the ones used to address hosts in an IP address. Class D addresses are used in multicasting.