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What you will do

  • Learn about Binary Numbers, bits, bytes and octets. Understand how an IP Address and Subnet Mask combine together to define a logical network segment.
  • Master calculating Broadcast and Network Addresses. Learn about Classful IP Addressing.
  • Become comfortable wth CIDR Notation, Route Summarization and various Subnetting problems.
  • Complete a large number of computer-generated problems with step-by-step hints and correction.

What you will need

  • A desire to master subnetting skills.
  • Basic math skills.

After taking this course you will

  • identify logical network segments based on an IP Address and Subnet Mask;
  • convert between decimal dot and CIDR notation;
  • perform subnetting calulations as required for real-world network deployment scenarios.
Comments & Discussion
Connected Dots Online6 days ago
It is becoming challenging to maintain this site as a free service. Starting February 1, 2023, continued access to all content will require a subscription. To keep the content as accessible as possible, subscriptions will initially start at USD 20 for one year of access.
New users will have access to a free trial before purchasing a subscription.
heroking3 months ago
After am done and master everything on the website, is there any website that is like this or what website should I go next?
Muhammad5 months ago
great content exactly how i like to study . one question do you have full networking and PC hardware related courses like this ? i have to get ready for CompITA A+ thanks
Muamer6 months ago
Hey guys, awesome course, really helped me understand networking. I have recommended this my coworkers and friends.
I know there have been a few questions about CCNA in the previous years but do you think this covers most of the CCNA cert?
Connected Dots Online6 months ago
Hi Muamer, thank you for the feedback! There is one section included in the CCNA that is not covered here yet - OSPF. Some OSPF content should start appearing in a couple of months from now. Thanks!
Daniel7 months ago
Great course, When will parts 7 and 8 be?
And when they came out, would it cover all the CCNA?
Thank you so much.
Connected Dots Online6 months ago
Hi Daniel, thanks for your feedback! Parts 7 and 8 should be available in a couple of months from now. Thanks!
Daniel6 months ago
Thank you!
Will it cover the CCNA after you add these parts?
Connected Dots Online6 months ago
It will cover all of the challenging topics on the CCNA exam. There will still be some content that you can read off the Official Certification Guide found here:
Santiago1 year ago
buenas esque esta prwegunta es imposible de responder porque yo pongo la respuesta correcta pero aun asi me dice que estaa mal : la pregunta esta en calculo de segmentos mas grandes:ejercicios y la direccion de red es 10 0 0 0 porfavor ayudenme que no puedo pasar de esta pregunta
Connected Dots Online1 year ago
Hola Santiago.. Si possible, podría enviar un email a "" con un "screenshot" del error? (incluya la pregunta). Gracias!
ckZA2 years ago
It's amazing how good this site is. As someone who values knowledge transfer at the best quality and where reasonable, free, I take my hat off to ConnectedDots.

When the internet came about it was for the betterment of our human race through sharing of knowledge and you feel that ethos (and magic) here.

Aaron2 years ago
Hey Quick question? Do you recommend using the sub-netting method you teach for the CCNA exams or would you recommend using sub-netting charts for these calculations under a time pressure? If so do you have any charts you recommend? Thank you very much - Aaron
Connected Dots Online2 years ago
Hi Aaron, please check your messages (top right hand corner of the screen) for a slightly longish answer to your question. Hope it helps!
Aaron2 years ago
This is my absolute favorite resource I've encountered. Better than the CCNA books or Video Courses that I paid a lot of money for. You're a legend!!! Thank you isn't enough.
Connected Dots Online2 years ago
Thanks for the feedback, Aaron! Great to hear that you found the content useful , and you're welcome! Best of the luck with the learning!
Asif2 years ago
Learning from this site is a real pleasure. A few days ago, I had no idea of computer networking and then stumbled upon this site somehow. And I love learning networking now. Thanks to your fantastic initiative!
I have a request to you. I want to learn wireless networking, WAN and broadband connections. I read a few books but didn't understand that much. I believe if you've made a few courses on these topics, many learners like me would be benefited.
Connected Dots Online2 years ago
Hi Asif,
Thank you very much for the feedback! There will be more content added over the next few months.
Asif2 years ago
I'm little confused with IP calculation with subnet mask. In the fourth octet, do we include network bits(as per subnet mask) for determining the host IP? Or do we leave the network bits alone and calculate host IP by changing other bits?
I saw the first instance in first module and saw the second one in the second module.
Connected Dots Online2 years ago
Hi Asif, we change only the host ID bits to determine the host IP; however, when calculating the decimal value of the octet in question, we have to convert all 8 bits of the octet into decimal to calculate the decimal equivalent.
BHANU2 years ago
Is Network Address Translation covered in the course?
Connected Dots Online2 years ago
Hi Bhanu, NAT is covered in the course on IP Services.
ALFRED2 years ago
Can someone help to solve the following questions :
[a] Suppose you have an address pool of Which subnet mask should you use ?
[b] The address is a valid host for which subnet ?
Connected Dots Online2 years ago
[a]: Start by figuring out how many addresses can be accommodated with each Subnet Mask. A subnet mask of (/29) will have 8 addresses. (/28) will have 16 addresses. (/27) will have 32 addresses.
Consider the address pool: .11 to .24 is 14 addresses in total. We might be tempted to think that a /28 (16 addresses) is the correct subnet mask.
However, with a /28, if we start at, the first network will go from - and the second network will go from -
The range of addresses to will span across 2 networks.
Therefore a /28 is not the correct subnet mask.
The next biggest network is a /27 ( The network /27 is the range of IP addresses - This range covers the entire pool ( - within one network.
The correct answer is
Connected Dots Online2 years ago
[b]: Start by calculating the network address for
The default subnet mask for the Class B networks is If the network is divided into smaller networks of size /21, which subnet (1st, 2nd, 3rd etc.) would fall into?
Shabir2 years ago
best courses that i have seen 1st time free with awesome simulator .It is 100 percent useful than online classes.
Connected Dots Online2 years ago
Thank you for your feedback, Shabir! Glad to hear that the material is useful!
Shabir2 years ago
thanks a lot
Bibek2 years ago
Does MAC adress plays any role during data transmission between network segments?
Connected Dots Online2 years ago
Hi Bibek,
Feel free to skip forward to the lesson "2.1 The Default Gateway" in the course "Routing Basics" for an answer to this question.
Bibek2 years ago
The ISP provides the router with public ip but the devices connected to the router have private ip. While communicating with the external internet, public ip becomes visible. How does the data gets transferred within the network ? Does MAC address has got to do anything with this?
Connected Dots Online2 years ago
Hi Bibek,
This is covered in the Course "IP Services" in the "Network Address Translation" section. If you follow the courses in order all the concepts will fall in place one after the other.
christian2 years ago
hi connected dots,help me understand the ip address with a subnet mask of how you determine its network address? From one of your tutorial you stated you will find the network address when all host bits are turned off which in this case we will have seven bits all off so i request you to help me understand the .128 as its network address.Please elaborate on your explanations,its my pleasure working with you.
Connected Dots Online2 years ago
Hi Christian, for the IP Address, with a subnet mask of, we know that the first 3 octets of the network address will be 192.168.100 (since the first 3 octets of the subnet mask are all 255).
For the last Octet, we start with the binary representation of 170:
170 (binary) => 10101010
The last octet of the subnet mask is 128:
128 (binary) => 10000000
To get the Network address, take the binary form of 170 (10101010) and match it up to the binary form of the last octet of the subnet mask:
170: 10101010
128: 10000000
The last 7 bits of the subnet mask are 0. Flip the last 7 bits of 10101010 to 0 and leave the first bit unchanged.
10101010 (make the last 7 bits 0) => 10000000
The last octet of the network address is 100000000 (binary)
10000000(binary) => 128 decimal.
The complete network address is

A quicker method to calculate Network addresses can be found in lesson "3.4 Calculating Network Addresses - Examples".
christian2 years ago
hi,i would really like to thank the creators of this course for helping a lot of people in this field improve their skills in networking.i would like to post a question on ip addresses, what is a network address ? Is it the part of the ip address that identifies the class of the network or is it the address assigned to group of computers in a network segment or is it the first ip address assigned to a computer in network segment.Please resonate with me based on those three i have mentioned.Looking foward to your response.
Connected Dots Online2 years ago
Hi Christian, thanks for the feedback. To respond to your question:
A network address is the portion of the IP Address that is common for all hosts on the network segment.
It is *not* the first IP address assigned to a computer in a network segment.
In the case of classful networks, you could say that the network address is the part of the IP address that identifies the class of the network.
NARENDIRA2 years ago
hello sir/madam!! I have a doubt in IP addressing and subnets
Q. Consider there are 3 networks as192.168.0.0/24192.168.64.1/26192.168.1.0/26Please say that if an IP address belongs to any of these networks?
My answer is yes and it belonged to the network192.168.0.0 as it ranges from to this correct, if not please justify the answer and clear my doubt. Thanks in advance.
I got this from some online site and that site shows answer as no that mentioned IP address does not belong to any of the networks mentioned above. I don't understand why it so. Please clear me with this one. 
Connected Dots Online2 years ago
Hi Narendira, the correct answer is no. /26: [ -] /26: [ -] /24 [ -] does not fall within any of those networks.
The range of addresses - would be the network
NARENDIRA2 years ago
Oh, thanks a lot!!
I calculated the address range for the network wrong by assuming the instead of as subnet mask expansion for that CIDR notation 24
Now got it thanks !!!!!
NARENDIRA2 years ago
And thank you so much for answering this I wrote in a very congested way as I typed in notepad properly then copy and paste the para from notepad to here so alignment changes, sorry for that.
Quiverus2 years ago
I'd like to ask, when we define a network segment, the Network Address's host bits should (or must they?) always be 0s, right?
Connected Dots Online2 years ago
Yes, you are correct, the host bits must all be 0 for a Network Address. The host bits must all be 1 for a broadcast address.
Quiverus2 years ago
All right, thank You for quick anwser!
sim2 years ago
Greattttt place to learn networking. i feel lucky that i end up here and now i can actually learn more because i get to practice myself. Thank you for such a great work!
Connected Dots Online2 years ago
You're welcome. Thanks for the feedback!
ALFRED2 years ago
Thanks very much for making this online courses available for newbies like me, to have something to study in my preparations for career switch from Telecommunications to Networking in my future roles
Connected Dots Online2 years ago
Thank you for your feedback, Alfred! Glad to hear that the content is useful!
ALFRED2 years ago
Under the Binary to Decimal Conversion, I noticed that from 4th bit to the 8th bit, it was 2 raised to the power of 3 that was used, even though correct answers were writen but mathematically it is not correct. Would like to know the reason , why it was so ,
Connected Dots Online2 years ago
Hi Alfred, could you please send a screenshot in an email to
That would help in clarifying your question.
Connected Dots Online2 years ago
Thank you so much for sending in the screenshot via email. You are correct, that was a typo in the lesson. It has now been corrected and updated. Thanks again for reporting it!
rimo2 years ago
i would like to help you become even more famous your courses just gave me all what i needed
Connected Dots Online2 years ago
Thank you for the feedback, Rimo. Please feel free to share the website with others! Thanks!
Dawit2 years ago
thanks for your quick answers...
Dawit2 years ago
why do we need to assign ip address in a single network segment when they can communicate using their mac address?
Connected Dots Online2 years ago
In essense, devices use both MAC Addresses and IP Addresses to communicate with each other. The MAC Addresses for a network interface generally remains constant, whereas the IP Address of the same interface can be changed as the device is moved from one network segment to another.
Also, it is difficult to remember MAC addresses. IP Addressing allows us to create logical network segments with easy to figure out addressing patterns.
The next course (Routing Basics) will help consolidate the relationship between MAC Addresses and IP Addresses.
Miguel3 years ago
Love It!!
Connected Dots Online3 years ago
Great to hear! Thanks!
Trân3 years ago
I had passed section IO Addressing & subnetting
introduction to network segments.
Connected Dots Online3 years ago
Trân3 years ago
When I finished for the Course list, I can test CCNA, That's right?
Connected Dots Online3 years ago
Hi Trân, this course list is a good beginning to get started on learning networking. As it stands currently, it does not cover everything that will be tested on the CCNA exam. Over the next few months we will be adding more courses to the course list that will cover the rest of the material that is tested on the CCNA exam.
Trân3 years ago
thanks so much. I hope that you can add in the CCNA Test.
jagbir3 years ago
is this addition done?
Connected Dots Online3 years ago
Hi Jagbir, we will not be adding an online CCNA exam. We will keep adding content to help learn and practice the content covered on the CCNA exam.
jagbir3 years ago
is the available content enough to crack CCNA exam
Connected Dots Online3 years ago
Hi Jagbir,
The content covered in this particular course should be sufficient to pass the subnetting portion of the CCNA exam. However, courses to cover other topics on the CCNA exam such as OSPF, RIP, IP Services, TCP/UDP are still under development.
Trân3 years ago
I am happy when I learn to this section, I am thankful you
Connected Dots Online3 years ago
Thanks for the feedback, Trân! You're welcome!
Shiv3 years ago
This is without a doubt the best interactive network training material. The methodoloy to teach is so simplistic yet interactive that even newbies can grasp the complicated concepts. There are plenty of examples and exercises to make sure you truly understand all concepts.

Thank you very much for creating such an unique way of teaching Networking concepts.
Connected Dots Online3 years ago
Thank you for your feedback, Shiv! You're welcome! Always glad to hear that the content helps to truly understand the concepts well.
Dmitry3 years ago
in the 1st chapter, "Introduction To Number Systems", it says, "the hexadecimal system employs numbers 0-7 and letters A-F". Isn't it "0-9"? That said, thank you very much for the course - really helpful!
Connected Dots Online3 years ago
Thanks very much for pointing out that mistake, Dmitry! You are correct, it should read "0-9". It has been fixed now. Thank you for your feedback as well. It's great to hear that the content is helpful!
akter3 years ago
Connected Dots Online3 years ago
Thanks for your feedback, Akter!
Sherzod3 years ago
Very good,thanks
Connected Dots Online3 years ago
Thank you for your feedback!