In the computer networks course, we solve subnetting questions together with the teacher. There is a term we call the "main network". As far as I understand, we fill in this according to whether the IP address is A, B or C class. But since classful IP addresses are no longer used today, what exactly does main network mean today? If it makes any sense, for example, how to find the main network of an IP address? I wanted to ask because it confused me as a student. Thank you in advance for your answers.

This is an example we used in the lesson: https://web.archive.org/web/20080405113738/http://www.brouckie.be/cgi-bin/IPsubnetting/index.pl


2 Answers 2


Based on your description, you probably mean the network address. That is the address where all the host bits are set to 0. It is used to refer to all the possible addresses as a whole.

You may find this question and answer helpful to your understanding.


Depending on context, the "main network" is either the network you start out with - e.g. or from RFC 1918 - or the smallest network supernetting all the others.

  • Thank your for your response. I am new to this topic and i am struggling too much. Because internet says something and my teacher says otherwise. Can you elaborate a little further for me to understand? Commented Apr 16 at 19:38
  • 1
    Read the link in the question above this one. That will explain in great detail.
    – Ron Trunk
    Commented Apr 16 at 19:53

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