> Subnetting Explained
Introduction
Simplified Subnetting, Let’s untangle the knots and dive into the world of networks.
Isn't it strange to see the IPv4 address of your laptop and IPv4 address you see on google are actually different ?
Identification used in the interconnected network.
A school identifies their students from admission numbers.
Each person has different telephone numbers.
Houses have addresses.
“Ah Ha, this all revolves around a primary key”. That’s the identification. Likewise the internet has IPv4 addresses. Although they are running out. Incredibly fast…
The bearer of IP addresses
Routers as we all know are middlemen. These devices are configured by ISP’s in your houses or office, to provide a connection, which enable devices to communicate with the internet, and browse various sources such as Netflix, or eBay.
So where’s your IP address ?
When you connect to a network such as your home Wi-Fi, each device is provided an IP addresses by DHCP (Dynamic Host Configuration Protocol) this is simply a software which is configured inside your router, and they act like a charity handing over each device an IP address.
What is an IP address?
Below is an IPv4 address, which is separated by decimals.
This is a 32-bit number, with 4 octets (1 octet = 8 bits = 1 byte) ) that are separated by a decimal. this is use to identify a device in a network. Like a house addresses
Since each bit could be 1 or 0 the maximum total of each octet will add up to 255 based on binary addition. This gives us 32 bits hence 1 bit could be 1 or 0 representing 2 states. We can calculate the IP addresses as 2^32 = ~4.3 billion
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As a result we can only have 2^32 IP addresses → Roughly 4.3 Billion IP addresses compared to a world population exceeding 7.6 Billion. How does the internet handle this?
Not the whole but even half the population accessing the internet there will have a shortage of IP addresses, as each IP needs to be unique
Why dont they just add more IP addresses? / A brief history
The internet “beeped” into life on the 1st of 1983. The internet along with the rules were minted, after all the entire network was hanging on this model, more specifically IPv4 addressing, nobody was ready for the change, definitely not during the internet Boom. on the other hand increasing addresses above the set limit would mean tearing down the bridge between 2 cities, so nobody dare changed it, but they did make the best of what they had or sort of...
It is like the school system, once made it never changed. The creators being IANA (Internet Assigned Numbers Authority) didn’t plan out well, by this what I mean is that they didn’t anticipate the internet boom.
Nowadays, from dog tags to Corporate institutes using servers, employ IP addresses. Hence, 4.3 Billion is no where enough.
Concept behind subnetting
To draw a parallel between this concept I’m going to explain. Suppose a school assigning each student a unique admission number. But the school software prevents you from reaching above 13 admission numbers, how do you solve this problem?
Normal - 1,2,3,4,5,6,7,8,9,10,11,12,13, error, error
For instance we can subset each number like such and incorporate decimals. The number before the decimal could represent their current grade, and under that grade we can provide the numbers after the decimal → 1.1,1.2,1.3,1.4,1.5 ….
(To clear things up this means a student in grade 5 will be listed as 5.x & a student in grade 7 will be 7.x)
The list goes on, you can see the point I’m trying to make here, this gives us access to a whole different sequence of numbers, a similar concept is applied to subnetting.
Classful Addressing
Each IP address falls under a specific class
Class A
- Class A is mainly used by ISPs (Internet Service Providers) IRs (Internet Registries), global companies rest are reserved by IANA (Internet Assigned Numbers Authority) and much more
- Roughly 16 million IP addresses on each network with 126 networks available
Class B
- Class B is used by medium-large scale companies, universities, government agencies to name a few.
- Roughly 65,000 IP addresses on each network, with 16,384 networks available
Class C
- Class C is used by small to medium-sized organizations, businesses, and home networks.
- 254 IP addresses on each network, with more than 2 million networks available
Class D
- Class D IP addresses are reserved for multicast (This is where one or many devices communicate with one or many devices)
Class E
- Class E IP addresses are used by research groups, military and other organizations
Enter the world of subnetting
As we saw in the previous example. IP addresses are divided further into IP classes to enforce priority and order within networks. Once we are talking about subnetting Classful IP addressing goes out of the park, we only refer to Classless IP addresses here
Let’s see how it works:
- Network ID—Identifies a network. The first several bits of a net ID, known as the class field or class bits, identify the class of the IP address.
- Host ID—Identifies a host on a network.
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Classless IP addressing
Once the network was divided into a number of segments, there was 1 major issue:
- Class A networks utilizing 16 million IP addresses, is a very much never occurring scenario. Because there wont be 16 million devices to a network at any one time, allocating this many addresses to a single network is a complete waste.
Issues as such posed limitations on the internet’s growth as there weren’t enough IP addresses
To counter this problem we further created smaller networks, this created further divisions under Classful IP addresses.
Today all IP addresses are Classless IP addresses, with the aim of maximizing efficiency, we now have the ability to make use of the 16 million IP addresses by assigning partitions into different networks.
Loopback IP addressing
The 127 IP address range is reserved in every PC (this is a Virtual IP addresses) that is used to ping itself ( this is used to identify whether a server/node is online or offline ). Known as the loop-back IP address (Hence it loops back to your device). Pinging is used for network testing there are 16 million addresses used to do this (Why this much? not sure but it is what it is )
Private Vs Public IP addressing
Until now all the IP addresses we have seen are publicly routed meaning that they can be accessible by anyone on the internet. However the internet couldn’t afford to provide this many IP addresses.
In order to counter this issue IANA released RFC 1918. This standard established Private IP addressing. These IP addresses are not router in the internet only within homes or local networks. How does this take place ?
When we connect to the home internet we are given an IP addresses to individually identify devices in a network. This is a Private IP addresses inaccessible to people outside the network, internet.
So how do we access the internet ? If they are not routed publicly ?
For this we make use of a Public IP address and this is the one IP address provided to us by the ISP. Due to the limited number of IP addresses, usually each router gets one Public IP addresses to explore the internet, and all devices in the network use the same IP to search the Web, although the IP within your home network is different, all devices use the same Public IP.
The conversion from private IP address to a Public IP address, is done by a protocol called NAT (Network Addressing Protocol). All of these settings and protocols are configured within your home routers.
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