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Editor to share with you unclassified addressing CIDR how to divide the network, I believe that most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

The first thing to know is what the CIDR is used to solve. We know that at first IP is divided into five categories, and we can use only the first three categories, but there are big problems with the division of these three categories. A Class B address can hold more than 60,000 hosts, while a Class C address can only accommodate more than 200 hosts. Such a classification will cause great problems, such as an enterprise with thousands of people, then Class C network certainly can not meet the demand, but Class B is too wasteful for it.

So? The IP classification has been eliminated and replaced by CIDR (no taxonomic addressing). The understanding of CIDR is also very simple, it is to use a subnet mask to split an IP into two, the front part is the network bit, the back part is the host.

Let's take a look at what the subnet mask is. The subnet mask, like the IP address, is made up of 32 bits, which is made up of consecutive ones before and consecutive zeros after them. We often use the decimal representation to display the subnet mask, as follows:

255.255.255.0

The subnet mask above consists of consecutive 24-bit 1s and consecutive 4-bit zeros. In addition, there is a common representation of subnet mask, which we call slash. As follows

192.168.110.121/24

The front is the IP address, and the last 24 represents the subnet mask. That is, it consists of a continuous 24-bit 1 and a consecutive 8-bit 0.

With the subnet mask, there are several other knowledge points, such as calculating the network number, broadcast address, the network can accommodate up to the number of hosts.

By manipulating the subnet mask and IP address, you can get the network number.

The last address of the network number is the broadcast address

The number of available addresses is related to the number of host bits, for example, if the host bit occupies 8 bits, then the number of available addresses is equal to the eighth power of 2, minus 2 (a network address, a broadcast address).

Next, let's consolidate what we have learned through a case, as follows, give the IP address and subnet mask, calculate the network number and other information.

172.16.1.196/20

We know the following knowledge

1 & 1 = 10 & 1 = 01 & 0 = 00 & 0 = 0

Then the question is simple. The first 16 digits must be the same, or 172.16, while the last 8 digits must all be 0. Therefore, we only need to do and operate the third part to get the answer.

The conversion from 1 to 2 in base 10 will result in

00000001

Calculate 0000000110000, the available value is 00000000, the conversion to 10 machine value is 0. So, get the network number as

172.16.0.0

Then calculate the number of available addresses, the host bit occupies 12 bits, then the available address is 2 to the power of 12 minus 2, that is, 4094.

The above is all the content of the article "how to divide the Network without classified addressing CIDR". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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