ComputerTipsLaiju

Subnetting 101 (Overview)

I will now be doing a subnetting tutorial in a nutshell in order to help those pips who are also inclined to my field. So first and foremost, let us start by defining some few terms. Some of the definitions are of my own words for simplicity’s sake and some might not be reflected in some books or reviewers. This tutorial is made with the assumption that the reader knows how to convert IP Address from Decimal to Binary or vice versa.

This is Decimal, 10.1.23.19.

This is Binary, 00001010.00000001.00010111.00010011.

The two IP addresses are identical but of different format.

Definition:

Network - a group of two or more computer systems linked together.

Subnetwork - is commonly called as subnet, is a subdivision of an IP network. Which in we use it in a pie analogy, the pie would be the network and the slices in the pie would be the subnetworks.

Subnet mask - a 32-bit combination that would describe the portion of the subnet and the portion of the host.

Host/User - a computer or another device that is connected to a network.

Prefix Length - is the number of bits set in the subnet mask. Your prefix length will determine you subnet mask. The reverse is also possible by converting your subnet mask to binary and counting the number of 1’s in the set.

Subnetting - the practice of dividing a network into two or more networks.

Sample Problem:

Ayala has a Network IP of 192.168.0.0/24. Ayala needs 3 subnetworks namely: Net A, Net B and Net C. Net A have 20 users. Net B have 10 users. Net C have 10 users. Provide the subnetworks that would accommodate Ayala’s needs.

Steps in Solving the Problem:

Given this question, we will now use the 5 basic fundamental questions in problem solving.

What is asked?

What is given?

What operation to be used?

What is your solution?

Is this your final answer?

What is asked?

The subnetworks that would accommodate Ayala’s needs.

What was given?

Network IP - 192.168.0.0/24

Net A with 20 users

Net B with 10 users

Net C with 10 users

What operation to be used?

Unlike in mathematics were we have multiple operations to choose from, we will be followings steps here instead of choosing operations. There is actually no sequence that was taught in the books or reviewers but I follow this sequence that I came to be quite fond of after four years of doing it. It is straight forward and easy to follow step that I put together.

Validate the Network IP

Why do we need to validate the Network IP? We need to verify if the Network IP is valid because some professors test their student’s analysis. Some professors will put an invalid Network IP so the problem will be invalid in an instant. Most students will just solve the problem without even considering if the problem was actually valid. This will result to waste of time especially during exams when you realize later after solving that the Network IP could not handle the client’s needs. (How to validate Network IP will be discussed in details in another post.)

Determine the biggest needed Network (Subnetting)

Now that you already validated your Network IP, you can start subnetting. In order to have a organize flow, we need to get the biggest needed network out of the client’s demand. In our sample problem that would be Net A since it has 20 users. (How to subnet a given IP will be discussed in details in another post.)

After subnetting the given Network IP, you will get 8 subnet IPs that could handle 30 users each with a prefix length of /27.

192.168.0.0/27

192.168.0.32/27

192.168.0.64/27

192.168.0.96/27

192.168.0.128/27

192.168.0.160/27

192.168.0.192/27

192.168.0.224/27

We will now assign the first set for our Net A. So our Net A will now be using the IP set - 192.168.0.0/27.

Technically, we can use the remaining sets to assign to Net B and Net C since each subnet IP could handle 30 users. But in making an effective network plan, this is considered a bad practice since you will be wasting 20 users resource on each subnet because you will only be using 10 valid IPs for each.

To correct this, we need to subnet again the next subnet IP ( 192.168.0.32/27 ) in order to maximize the resource that we have.

After subnetting the next subnet IP, you will get 2 subnet IPs that could handle 14 users each with a prefix length of /28.

192.168.0.32/28

192.168.0.48/28

We will then now use these two subnet IPs with 14 users capacity to our remaining needed networks which are Net B and Net C.

What is your solution?

From our subnetting process. We can now produce a solution which is:

192.168.0.0/27 - Net A

192.168.0.32/28 - Net B

192.168.0.48/28 - Net C

Is this your final answer?

Normally, this is an enough solution and your professor will already understand this. However, as a student, we need to secure our grade so just to be on the safe side we will need to dissect this into a more detailed solution.

How? We simply present it in this format:

General IP: (Given Network IP) Network Name: (Given Needed Network) Network IP: (Subnetted IP for this Network) First Usable: (First Usable IP of this Subnet) Last Usable: (Last Usable IP of this Subnet) Broadcast: (Broadcast Address of this Subnet)

So our final answer will look like this:

General IP: 192.168.0.0/24

Network Name: Net A Network IP: 192.168.0.0/27 First Usable: 192.168.0.1/27 Last Usable: 192.168.0.30/27 Broadcast: 192.168.0.31/27

Network Name: Net B Network IP: 192.168.0.32/28 First Usable: 192.168.0.33/28 Last Usable: 192.168.0.36/28 Broadcast: 192.168.0.37/28

Network Name: Net C Network IP: 192.168.0.48/28 First Usable: 192.168.0.49/28 Last Usable: 192.168.0.62/28 Broadcast: 192.168.0.63/28

And there you go! This is an overview of how you will solve a subnetting problem. (How to determine the FUA/LUA/BA will be discussed in detail on another post.)

Me: “How long?” Dude: “As short as possible” Me: “Sure thing buddy”

I don’t know how recently this started, but today I have discovered that tech media website CNET as well as its website download.com have started trying to sneak adware into the computers of people who try to download legitimate software from their sites.

I didn’t have a rar expander (this is a very new computer) and needed one immediately so I quickly grabbed one off of CNET’s website.

I will tell you the story from a Mac user’s point of view. (Windows users, beware anyway): instead of giving you the developer’s installer, CNET gives you its own CNET Installer.app.

when I ran the application, not only did it install the rar expander as intended, but it also installed a number of strange extensions on each of my browsers, and set each browser’s search engine to yahoo and the homepage to some yahoo search result for ‘spigot’, which is the name of the adware company that developed these extensions. 

I have recently made a commitment to start reading terms of use and software license agreements, but this time i didn’t because I was in a hurry. Had I read them I would have seen that they would have asked me to agree to their installing these extensions and changing my browsers.

To get rid of the software, open each of your browsers and delete the strange extensions. Then set the homepage and search engine settings to back the way they were. Then go to ~/Library/Application Support/ and delete the directory 'Spigot’.

After three years of studying computer science/engineering at university I think I can make a sort of post about this matter. There are some misconceptions about IT degrees. So many. In the following lines, I’ll try to put together the main ones I currently have faced. I’ve been asked to make a post like this some time ago, so here it is. I’m focusing on computer science/computer engineering since it’s what I am studying.

The summer before I started my first year of university I was freaking out. Not only did I go to study at university but also I was going to study computer science/engineering! I love computers and that, but little did I know about computers to be honest. So my first thought was what computer should I buy. And here we go with the classic macbook vs laptop battle. My dad bought me a laptop so I didn’t think about really about this (as a note, it’s not the best laptop, but it’s enough at least for now). If you are wondering what computer should you buy for computer science, but you whatever you like the most, but I suggest you to have in mind that it doesn’t matter if you choose a laptop or a macbook. If you have enough money and you want a macbook, go for it. If you don’t or you don’t like macbook, you have other options. Choose wisely.

I was told that I would be the only girl in the class. Well, so the first day of university came and I couldn’t see a single girl in the hall. It turned out that there were about 12 girls in my class and about 80 boys (depending on the class). In my last semester I’ve been in a class where I was the only girl and as a consequence of several classes being minority, I get used to be the only girl and I felt stronger someway.

One thing more I was told it was that people on this degrees were a bunch of nonsocial, unatracttive and weird genius. To be honest this was something that scared me too, because I didn’t want to be alone. But again, this was untrue; of course, there are a few weird people, but mostly of them are nice people. I haven’t still seen a genius, just hard-working people.

I realized since the very beginning of my academic journey that when I told people what I am studying, there are three reactions I can observe in people:

The “pfff, that’s a difficult degree” reaction.

The “pfff, that’s a difficult degree for a woman” reaction.

The *open the mouth for a while and say nothing* reaction.

“But is computer science or computer engineering difficult?”, that’s another thought that made me head spin. All right, it is. I am not going to lie. It is difficult. Really difficult, but once you get the hang of studying, organizing and thinking, everything will be easier. Personally I wasted a year trying to learn how to think and study for the classes. I was stuck into the high school habits and I didn’t want to change them. If I have learnt something about university (or life) is that you have to be ready for switching and don’t be afraid of changes.

“I would like to work as a computer scientist/computer engineer/software engineer/… but I’m not good at mathematics/physics/…”. Okay, computer science/engineering is difficult but not that hard (I may slightly lie in the aforementioned question, except calculus, calculus is evil). I mean, professors start with the very basics of every class, and it isn’t usually very difficult. Plus most of them are willing to clear up your questions in office hours. I have some friends who are really bad at maths and they have passed all the algebra and calculus classes. Also I have friends that didn’t want to study an IT degree, though they’d love to, because of this reason. Don’t be the person who didn’t study something because of a few hard classes. You’ll regret later.

After a couple of month, studying computer science/engineering, some people start wondering why we are studying physics, electronics and math, “when are we going to start hacking?”. Oh, well. That’s a good question. Never. WE DON’T LEARN TO HACK in university. In my first year, many classmates drop out of computer science because of this single reason. They thought they’ll learn how to hack.

“At least, I will code a lot!”. Sorry again, but you are going to be programming less than you would expect. At my university, we take only 6-7 classes focused on just programming in the four years of the degree.

When you assume that most of the things you believe are not true, you’ll know more or less if you like this degree or you don’t. At the same time, people are going to ask for help. Yes, the “can you fix my [insert here ANY electronic device]?” and “can you tell me how to [any action] in [any program or website]?”. You can’t get away of these questions. Believe me or not, but if you get involved in an IT degree you are not going to study how to delete a Facebook account. You may or not may be surprised of this, but a great amount of people has asked me this question. Plus, we don’t learn how to fix smartwatches. Surprise!

At this point, people wonder what the hell computer science/engineering is about. Algebra, calculus, physics, electronics, robotics, algorithms, AI, data structures, computer security, networks, computational complexity,…