Subnetting is one of the most important network lessons. It is especially important for entry level network engineers. Network engineers learn this lesson and how to calculate subnet mask at the beginning of many different certification paths. For Cisco CCNA Certification, Huawei HCIA, Nokia NRS I and Juniper JNICIA, it is very important and key lesson. So, network engineers need to know some special parts of subnetting. To overcome this, network admins use subnetting cheat sheet. Subnetting cheat sheet includes almost all necessary information for this calculation. 

To practice on this lesson, there are different questions. In such questions, basically an IP address is given with a subnet mask and the usable ip addresses are calculated. Sometimes the required ip addresses can be host ip addresses and sometimes it is broadcast ip address or network addresses. Whatever it is, if you learn how to solve a subnetting question, then you will successfully achieve it. During this period, a cheat sheet will be a perfect tool for you. You can check the required subnet masks and determine the ip addresses quickly with this cheat sheet. Beside you can learn special ip addresses like private block ip addresses, bogon ip addresses, APIPA ip addresses etc. 

If you would like to pass the entry level certifications like Cisco CCNA Certification, Huawei HCIA, Nokia NRS I, uniper JNCIA, you should learn subnetting very well. Almost all CCNA books cover subnetting with many examples and scenarios. 

Subnetting Examples

So, to understand subnet masks let’2 given some examples for this lesson. Below, you will find important subnetting question examples.

Subnetting Example 1

We have an IP prefix 100.45.74.0/27. How can we calculate the usable ip addresses for the host for this ip prefix?

To learn CIDR value /27, let’s check subnetting cheat sheet. On this cheat sheet, you can see that, we can have 5 bits for host parts and this means that we will multiple 2, five times (2 x 2 x 2 x 2 x 2). The result of this calculation will be 32. But this is the available ip addresses not usable ip addresses. We can divide network and broadcast ip addresses from these ip addresses. So, we will have 32-2=30 urable host addresses. These are:

100.45.74.1
100.45.74.2
100.45.74.3

100.45.74.30


Subnetting Example 2

We have an IP prefix 200.4.70.0/29. How can we calculate the broadcast ip address of this ip prefix?

To do this calculation, we can check our subnet cheat sheet again. The CIDR value is /29. This means that we have 32-29=3 bits for host parts. This means that 2 x 2 x 2 = 8 ip addresses total.

The first ip address is network address and the last ip address is broadcast ip addres. 
200.4.70.0    network ip address
200.4.70.7    broadcast ip address

The other ip addresses between these ip addresses are usable host addresses. 

Important Lesson For Certifications

As we have mentioned before, subnetting is a key lesson for almost all entry level certifications like CCNA Certification, HCIA Certification, JNCIA Certification and Nokia NRS I Certification. If you learn this lesson very well, you can easily solve subnetting questions and you can sue this information in your network operations. This lesson is also a key lesson for Cisco CCNA books and courses.  To do this, you can also benefit from cheat sheets, like subnetting cheat sheet.