Classes of IP addresses (IP Classes)

In the early days of the internet, IP address was based on IP classes. IP classes were used to define how IP addresses were allocated and managed. IP classes have largely been replaced by CIDR notation, but it’s still useful to understand the concept of IP classes.

There are three primary IP classes: A, B, and C. The IP address is divided into four octets, and the value of the first octet determines the IP class. Each class has a different range of IP addresses that can be assigned to hosts.

IP Class A

IP class A addresses are used for networks that have a large number of hosts. The first octet of an IP class A address is in the range of 1 to 126. The remaining three octets can be used to address hosts on the network. This means that there are 126 possible class A networks, and each network can have up to 16,777,214 hosts. The total number of hosts that can be addressed using class A addresses is 2,113,929,216.

IP Class B

IP class B addresses are used for medium-sized networks. The first octet of an IP class B address is in the range of 128 to 191. The first two octets are used to address the network, and the remaining two octets are used to address hosts on the network. This means that there are 16,384 possible class B networks, and each network can have up to 65,534 hosts. The total number of hosts that can be addressed using class B addresses is 1,073,741,824.

IP Class C

IP class C addresses are used for small networks. The first octet of an IP class C address is in the range of 192 to 223. The first three octets are used to address the network, and the remaining octet is used to address hosts on the network. This means that there are 2,097,152 possible class C networks, and each network can have up to 254 hosts. The total number of hosts that can be addressed using class C addresses is 536,870,912.

There are two additional IP classes, D and E, that are reserved for special purposes. IP class D addresses are used for multicast traffic, while IP class E addresses are reserved for future use.

IP class D

IP class D addresses are used for multicast traffic. Multicast traffic is a type of network traffic where data is sent from one source to many recipients at the same time. For example, streaming video or audio content over the internet may use multicast traffic to send the data to multiple viewers simultaneously. IP class D addresses range from 224.0.0.0 to 239.255.255.255.

IP class E

IP class E addresses are reserved for future use and are not currently used on the internet. IP class E addresses range from 240.0.0.0 to 255.255.255.255. These addresses are reserved for experimental or research purposes and are not available for general use.

Here’s a table that summarizes the IP classes and their address ranges:

IP ClassAddress RangeDefault Subnet MaskMaximum NetworksMaximum Hosts per Network
A1.0.0.0 to 126.0.0.0255.0.0.012616,777,214
B128.0.0.0 to 191.255.0.0255.255.0.016,38465,534
C192.0.0.0 to 223.255.255.0255.255.255.02,097,152254
D224.0.0.0 to 239.255.255.255Not ApplicableNot ApplicableNot Applicable
E240.0.0.0 to 255.255.255.255Not ApplicableNot ApplicableNot Applicable

It’s important to note that IP classes have largely been replaced by CIDR notation, which provides a more flexible and efficient way to allocate IP addresses. CIDR notation allows network administrators to allocate IP addresses in smaller blocks, which makes it easier to manage IP address space and reduce waste. Nonetheless, understanding the concept of IP classes, including class D and E, is still important for understanding how IP addresses are assigned and used on the internet.

IP classes have largely been replaced by CIDR notation, which provides a more flexible way to allocate IP addresses. CIDR notation enables network administrators to allocate IP addresses in smaller blocks, which makes it easier to manage IP address space and reduce waste. Despite this, it’s still important to understand the concept of IP classes, as it provides a foundation for understanding how IP addresses are assigned and used on the internet.

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