Subnetting: Definition
Breaking the larger network into smaller sub-networks is called subnets. Subnetting is the method of stealing bits from the HOST portion of an IP address. We end up with NETWORK SUBNET HOST fields after subnetting. To identify the subnet and another one to identify the broadcast subnet address, we always reserve an IP address.
Subnets: Used for
To help minimize network congestion, subnets provide a way of organizing the network. It will help to group those sections into a single segment if you have a lot of traffic traveling between specific parts of your network, so the traffic does not have to move across the whole network to get from place to place. Separating small sections of the network into subnets helps traffic to flow quicker, inserting traffic where it is not required to avoid taking unnecessary routes.
Subnetting also helps to assign IP addresses easily and prevents vast numbers of IP addresses from being unused. For specific offices or specific teams within an organization, subnets are typically set up geographically to allow their network traffic to remain within the location.
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Three Reasons for Subnetting
IP address conservation: Imagine having a network of 20 hosts. A lot of IP addresses (254-20=234) would be lost by using a class C network. It will be more productive to split up large networks into smaller parts and maintain a large digit of addresses.
Reduced network traffic: The smaller networks that produce the minimal broadcast domains are established, resulting in less network boundary broadcast traffic.
Simplification: By isolating network issues down to their fundamental nature, splitting large networks into smaller ones may simplify fault troubleshooting.
Pros of Subnetting
- Get your network arranged
- Reduction of congestion
- Avoid unsubscribed IP labels
Organizing and Optimizing the Network Using Subnets
Essentially, a subnet under class A, B or C is a smaller portion of the network. Creating and using subnets will help keep your network functional and structured.
Let's say that a company wants to use four separate IP address blocks, with 50 hosts per segment, for the various segments of its network. The organization utilizes the following blocks of IP addresses:
200.1.0.0
200.1.1.0
200.1.2.0 0
200.1.3.0
Each IP address block will generate 254 IP addresses, allowing the sum of 254 x 4 total IP addresses for network use. That corresponds to 1,016 IP addresses. But on each block, the company only needs 50 hosts, so it'll have 816 IP addresses that don't get used at all. That is a waste of IP addresses that other devices might use. Subnetting is a way to split a block of IP addresses into smaller pieces, such that fewer IP addresses are wasted.
We know that the network portion is 200.1.0.0, 200.1.0 for the first IP address, and .0 for the host portion. In the 32 binary bits, the complete IP address will look like this:
11001000.00000001.00000000.0000000000
But we know that we don't need all the 254 hosts that this IP address block produces, so we can borrow some of the "bits" of the host to create a new "subnetwork," or subnet.
Using the example of 11001000.00000001.00000000.00000000, we will borrow one "bit" to create a subnet from the host part.
So:
11001000.00000001.00000000.0000000000
Will have become:
11001000.00000001.00000000.10000000
As a consequence, it will become the current decimal IP address:
200.1.0.128
In the host segment, borrowing this one bit from the host portion of the IP address still leaves seven bits. For the most part, seven bits allow the development of 128 IP addresses, which is still more than enough for the demands of the corporations. If we follow the process and borrow another bit from the IP address host part, it is possible to have four subnets.
11001000.00000001.00000000.00000000. 200.1.0.0 200.1.0.0
11001000.00000001.00000000.01000000 200.1.0.64
11001000.00000001.00000000.10000000 200.1.0.128
11001000.00000001.00000000.11000000 200.1.0.1922
These four subnets allow the development of 64 IP addresses, and there is much less wastage than in the above example.
For the network identity itself (the first IP) and the broadcast address, there are two hosts reserved for the IP addresses required (the last IP). So, only 12 IP addresses are misused for each IP address block.
That is where masks from the subnet come back in. If bits from the host portion of the IP address have been "borrowed," it can be hard to say where the network portion ends and the host portion starts.
For instance, for the above-created IP address 200.1.0.64, the subnet mask would be:
11111111.11111111.11111111.1100000 (subnet mask 255.255.255.192)
11001000.00000001.00000000.01000000 (IP address 200.1.0.64 in binary)
The '11' means that the first two bits of the host portion of the IP address belong to the subnet, instead of the host, at the beginning of the final portion of the subnet mask, which results in the '192' portion.
How to do Subnetting (or the Concept of Subnetting Explained)
To better understand the subnetting definition, imagine a network with a total of 256 addresses (a Class C network). One address is used to identify the network address. the other is used to identify the broadcast address on the network. We are therefore left with 254 addresses available for hosts to address.
We still maintain the total number of original addresses if we take all these addresses and split them equally into eight separate subnets, but now we have divided them into eight subnets with 32 addresses in each. For the subnet and broadcast address within the subnet, each new subnet must dedicate two addresses.
The result is that we finally have eight subnets, each of which has 30 subnet addresses accessible to hosts. You will see that the total number of addressable hosts is reduced (240 instead of 254), but the addressing space is managed.
Calculate the Number of Subnets Available
Issue Question
How many subnets and hosts will you get per subnet from the 172.30.0.0 255.255.255.240 network?
Calculations
The following steps calculate our answer:
Calc the bits in the subnet. 172.30.0.0/28:
Net bits = 16bits. 16bits.
Bits of the host = 4bits.
Bits of the subnet = 12bits.
The total number of subnets is 4096 (based on 12bits)
Max per-subnet hosts.
Give us your magic number. 256 - 240 = the 16th.
Minus 2 (1 for the number of the network and 1 for transmission) = 14.
ANSWER
Subnet Total = 40966
Complete (per subnet) hosts = 14
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