Now
a days we have lots of subnet calculator available in Internet. But
learning subnetting is still a "must" for network engineers. The one and
only way to learn subnetting is "Subnetting Practice".
Before
learning subnetting you have to know some basic terms, like what is
network bits, host bits, what is subnet mask. There are many definitions
of these terms. But below I'll give some simple and short
definition/explanation of them.
IP address: Simply IP address is an address which is used in internet world to address a device. Every single device connected to internet must have an IP address. There are two version of IP address. But now we will focus on IP version 4. This version has 32 bits or 4 octets.
Class of IP: All the IP address are divided into 5 different classes. But now we will know about first three class.Class is determined by the first octet of IP address. Class A (range 0-127), Class B (range 128-191) and Class C (range 192-223).
Network Bit and Host Bit: There are two parts of an IP address. The first part is Network part. Bits of this part are used to indicate the network address and these bits are called Network Bits. The second part is Host part. Bits of this part are used to indicate the addresses of host, which are connected with that network and these bits are called Host Bits.
Subnet mask: To indicate the network portion and host portion of an IP address a masking technique is used. This mask is called Subnet Mask. In this system, every network bit is replaced with 1's and every host bit is replaced with 0's.
CIDR Slash Notation: This notation is used instead of Subnet mask. Its written after the IP address preceding a slash. It is the number of network bits of the IP address.
Now an example will help to understand. Consider a meaningless series of number like 192.16.0.0. Notice that this number has 4 part or octet. So we can call it an IP address. Now notice the first octet. It is 192, which is between the 192-223. So we can call it a Class C IP address. Now suppose you asked the provider how many network bits and host bits this IP address has. He answered 11111111.11111111.10000000.00000000 (in binary) or 255.255.128.0 (in decimal). His answer is not direct and clear to you. So you can assume that it is a Subnet Mask and count the number of 1's. There is 17 1's. Now you know that this IP address has 17 bits in its network portion and 15(=32-17) bits in its host portion (as it has 32 bits in total). Now if you want to avoid that lengthy subnet mask, then you can use CIDR slash notation like this "/17" So finally you can write that meaningless series of number like this 192.16.0.0/17. Now you have learned the basic of IP address and per-requirements of IP subnetting. So Can we start?
Here we will learn subnetting by solving a model question of CNAP skill final exam. If you don't have it, you can download it from here http://cthefusion.blogspot.com/2013/08/ccna-1-skill-final-practice-questions.html.
I solved that Model Question and described the process. So its a little
bit long. Don't be confused or depressed. Read every line carefully and
pay special attention to the marked line or words. Then practice more
and more. Now download the solution manual from the link, provided
below.
If this link doesn't work, then paste it to your browser address bar.
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