How to understand network addresses and sub-net addresses in the learning material of AZ-104

Copper Contributor

Hi Everyone,


I am currently studying for the AZ-104 Certification using Microsoft Learn.


My greatest challenge is learning the Networking component of the learning material.


I am confused by the way that sub-nets are presented in the learning material. With my understanding of networking a network should not have a different mask to a sub-net.


Here is an example screen capture from the learning material -




Given the above example IPv4 address space the mask is -




which in binary is -




which in Decimal is -


This network mask should allow for the following sub-nets -


Can anybody explain how the sub-net (in the screen capture) factors in?


Kind Regards,




3 Replies
best response confirmed by MrDavo75 (Copper Contributor)

Hi @MrDavo75,

In the example screenshot you shared, the IPv4 address space is shown as This means that the subnet mask for this network is /20, which translates to in decimal format.

Now, you're right that with this subnet mask, you should be able to have a range of subnets like,,, and so on. But here's where it gets a bit tricky in the screen capture.

They mention a specific subnet,

The /24 subnet refers to a subnet mask of, which is different from the /20 subnet mask.

So, this /24 subnet has a smaller range of IP addresses within the larger /20 network. It goes from to, with the first and last addresses reserved for network and broadcast addresses.

Basically, what they're showing in the example is different subnets within the overall network address space of Each subnet can have its own subnet mask, allowing for more precise network segmentation and addressing.

*I will give you one more example (to better understand the subnet part) if i can write it understandable for you:

Imagine that you have a company with multiple offices located in different cities (countries).
Each office needs to have its own separate network.

Let's focus on one particular branch office, which we'll call Branch A.

The network address space for Branch A is This means that the network can have a range of IP addresses starting from to

Within Branch A, there are different departments that require their own dedicated subnets:
For example, the Sales department needs its own subnet. Let's assign the subnet to the Sales department.

Now, with the subnet mask /24, which is equivalent to, the Sales department has an IP address range of to This allows for up to 254 devices within the Sales department to be assigned unique IP addresses.

Similarly, other departments within Branch A, such as HR or IT, can have their own subnets with their respective IP address ranges. Each subnet can be configured with its own subnet mask based on the number of devices expected within that department.

By using subnets, you can logically divide the larger network into smaller segments, allowing for better organization, security, and efficient IP address allocation.

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Kindest regards,

Leon Pavesic

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