Inside Azure Networking: How I Created a Virtual Network with Custom Subnets

If you've ever stared at the Azure portal wondering where to even begin with networking, you're not alone. I was right there a few weeks ago. In this post, I'm walking you through exactly what I did — from creating a resource group to building a virtual network with three custom subnets. No fluff, just real steps with real screenshots.

Let's get into it.

Head over to portal.azure.com

Once logged in,

💡 Quick note: I covered resource group creation in a previous blog too, but I'm including the steps here again so this post is fully self-contained. No jumping around needed.

Step 2 — Create a New Resource Group

Once you're on the Resource Groups page, you'll see a list of any existing groups or an empty list with a create button visible on the page. To create a new one, click the + Create button at the top left.

Step 4 — Review and Create the Resource Group

You'll be taken to a summary screen. Confirm the details look right — subscription, name, and region. Then hit the Create button at the bottom.

Step 6 — Search for Virtual Networks

Now that our resource group is ready, it's time to create a Virtual Network inside it. Use the top search bar again and type "virtual networks". Click on Virtual networks from the Services dropdown.

Step 8 — Fill in the Virtual Network Basics

On the Basics tab of the creation wizard, configure the following:

Subscription — Azure subscription 1

Resource group — Select the Netaccess group we just created

Virtual network name — I named it Netaccess-VM

Region — (Africa) South Africa North

Then click Next to move to the next tab.

Why delete the default subnet? Because accepting defaults means Azure names and organises things on your behalf. When you create your own subnets from scratch, you control the naming convention, IP ranges, and how traffic is logically segmented. Clean slate = cleaner architecture.

Step 10 — Review and Create the Virtual Network

Click through to the Review + create tab. You'll see a green "Validation passed" banner at the top — Azure confirming everything looks good. Take a moment to review the summary:

Subscription: Azure subscription 1 ✅

Resource Group: Netaccess ✅

Name: Netaccess-VM ✅

Region: South Africa North ✅

Security (Bastion, Firewall, DDoS): all Disabled ✅

Hit the Create button at the bottom.

Step 12 — Explore the VNet Overview and Navigate to Subnets

You're now inside the Netaccess-VM virtual network overview page. You can see all the essentials — resource group, location, address space (10.0.0.0/16), and notice it currently shows 0 subnets (because we deleted the default one earlier).

In the left sidebar under Settings, click on Subnets. This is where we'll build all three of our custom subnets.

Step 14 — Add Subnet 1 (Netaccess-subnet1)

The "Add a subnet" panel slides in from the right. Fill in the following:

Subnet purpose — Default

Name — Netaccess-subnet1

IPv4 address range — 10.0.0.0/16 (this is auto-populated from your VNet address space)

Starting address — 10.0.0.0

Size — /24 (256 addresses)

This creates a subnet range of 10.0.0.0 - 10.0.0.255. Leave IPv6 unchecked and scroll down to click Add.

Notice how we moved the third octet from .0.0 to .1.0 for the second subnet — that's how we keep each subnet in its own separate IP block within the same /16 space. No overlap, no conflict, no headaches so we do the same to create Netaccess-subnet3.

Step 16 — All Three Subnets Created Successfully

Repeat the same process one final time for the third subnet:

Name — Netaccess-subnet3

Starting address — 10.0.2.0

Size — /24

After saving, your Subnets page will now show all three subnets neatly listed with their IPv4 ranges highlighted:

NameIPv4 RangeAvailable IPsNetaccess-subnet110.0.0.0/24251Netaccess-subnet210.0.1.0/24251Netaccess-subnet310.0.2.0/24251

Summary

Here's the full recap of what we did:

✅ Searched for and opened Resource Groups

✅ Created the Netaccess resource group in South Africa North

✅ Searched for and navigated to Virtual Networks

✅ Filled in VNet Basics — name Netaccess-VM, resource group Netaccess

✅ On the Address space tab, deleted the auto-generated default subnet

✅ Reviewed and created the Virtual Network (validation passed)

✅ Deployment completed — clicked Go to resource

✅ Navigated to the Subnets section inside the VNet

✅ Clicked + Subnet to start adding custom subnets

✅ Created Netaccess-subnet1 → 10.0.0.0/24

✅ Created Netaccess-subnet2 → 10.0.1.0/24

✅ Created Netaccess-subnet3 → 10.0.2.0/24

✅ Cleaned up both Netaccess and NetworkWatcherRG resource groups

Why This Matters

Understanding how to manually structure your subnets gives you real control over how traffic flows in your cloud environment. Instead of accepting defaults, you're deliberately choosing IP ranges — which becomes crucial when you start doing things like:

Separating frontend and backend application tiers

Connecting on-premises networks via VPN Gateway or ExpressRoute

Setting up Network Security Groups (NSGs) with rules per subnet

Deploying services that require dedicated subnets (like Azure Bastion or App Gateway)

This is foundational Azure networking.

If this helped you, drop a ❤️ or leave a comment — especially if you ran into something different in your own setup. I'd love to hear about it.

Until next time — keep building! 🚀