subnet masks

gentlemen, how do i read this?
172.16.2.0/24

gentlemen, how do i read this?
172.16.2.0/24

It would be interpreted as:
IP Address: 172.16.2.0
Subnet Mask: 255.255.255.0

Since the IP Address is a Class "B" Address & the Default Subnet mask for this class is 255.255.0.0, so there are 8 extra bits being used for subnetting.

So, in a nutshell, here is what it means:

172.16.2.0 is a classless IP.
/24 means there are 24 bits being used to represent the network portion which means that the subnet mask is 255.255.255.0 which inturn means there is a subnetting of 8 bits.

thanks tarun

Tarun is correct in that subnetting can be done by using only one host bit. My comments were intended to stay in the context of classful subnetting. Only classless routing protocols would properly interpret classless subnetting. In other words if you are using RIP or IGRP borrowing only one bit will lead to definite routing problems.

This is not a “cisco” thing. It is understanding the difference between classful and classless routing protocols and distinguishing the difference in the subnetting rules required for each.

My comments were intended to stay in the context of classful subnetting.

And i thought subnetting is only classless. I have never heard anything about classfull subnetting :shock:

This is not a “cisco” thing. It is understanding the difference between classful and classless routing protocols and distinguishing the difference in the subnetting rules required for each.

What are the subnetting rules required for classful routing protocols like RIP1 ?

Thanks in advance

dear mew, i have to agree with tarun on the fact that there is nothing known as classfull subnetting. the moment you set a subnet mask you detach yourself away from a classful IP address which has a default subnet mask. to recall, an ip address which has a default subnet mask is called a classful IP address, the moment you are setting a new subnet mask for it, it loses its classful identify and becomes a classless IP address. i am sure tarun will agree on this.