Number of Network address in Class-C of Ipv4

In the IPv4 addressing format, The number of networks allowed under the Class C address are:

A) 2¹⁴         B) 2⁷         C) 2²¹          D) 2²⁴

This Question is asked in GATE-2012 (CS) Exam

Every class in IPv4 addressing has fixed format to specify IP - Address. Below is how the addresses are divided among the classes

Class-C IP address will have the following format

• First 3 bits are fixed as 110.
• Next 21 bits represent the Network-ID and last 4 bits represent the host-ID.

Since 21 bits are reserved for Network addresses. The total number of unique addresses possible in IPv4 Class-C is 2²¹. (The total size of Network-ID field is 24 out of which first 3 bits are fixed)

Hence, the correct answer is C)

Note that in IP Addressing, the Network ID identifies a specific network or subnet, while the Host ID identifies a specific device (host) within that network.

Further Explanation of IP Address Components

Example:

Consider the IP address 192.168.1.100 with a subnet mask of 255.255.255.0:

• The Network ID is 192.168.1.0, which identifies the network to which the device belongs.
• The Host ID is 100, which identifies a specific device (the host) within that network.