Subnets within a VNet in Azure - Mini Project: Build & Apply

Subnets within a VNet

📖 Scenario: You are setting up a simple network in Microsoft Azure. You want to create a Virtual Network (VNet) and divide it into smaller parts called subnets. This helps organize and secure your cloud resources.

🎯 Goal: Create an Azure Virtual Network named myVNet with the address space 10.0.0.0/16. Then create two subnets inside this VNet: subnetA with address prefix 10.0.1.0/24 and subnetB with address prefix 10.0.2.0/24.

📋 What You'll Learn

Create a Virtual Network resource named myVNet with address space 10.0.0.0/16.

Create a subnet named subnetA with address prefix 10.0.1.0/24 inside myVNet.

Create a subnet named subnetB with address prefix 10.0.2.0/24 inside myVNet.

💡 Why This Matters

🌍 Real World

Organizing cloud resources into subnets helps manage security and traffic flow in real Azure environments.

💼 Career

Understanding how to configure VNets and subnets is essential for cloud engineers and network administrators working with Azure.

1

Create the Virtual Network

Create an Azure Virtual Network resource named myVNet with the address space 10.0.0.0/16. Use the addressSpace property to set the address range.

Azure

# Define the Virtual Network resource
# Your code here

Hint

Use the addressSpace property inside properties to set the VNet's address range.

2

Add the first subnet

Add a subnet named subnetA with address prefix 10.0.1.0/24 inside the subnets list of myVNet. Add it as an object with name and properties.addressPrefix.

Azure

{
  "type": "Microsoft.Network/virtualNetworks",
  "apiVersion": "2021-05-01",
  "name": "myVNet",
  "location": "eastus",
  "properties": {
    "addressSpace": {
      "addressPrefixes": [
        "10.0.0.0/16"
      ]
    },
    "subnets": [
      {
        "name": "subnetA",
        "properties": {
          "addressPrefix": "10.0.1.0/24"
        }
      }
    ]
  }
}
# Your code here

Hint

Add the subnet object inside the subnets array with the correct name and addressPrefix.

3

Add the second subnet

Add a second subnet named subnetB with address prefix 10.0.2.0/24 to the subnets list in myVNet. It should be a separate object alongside subnetA.

Azure

{
  "type": "Microsoft.Network/virtualNetworks",
  "apiVersion": "2021-05-01",
  "name": "myVNet",
  "location": "eastus",
  "properties": {
    "addressSpace": {
      "addressPrefixes": [
        "10.0.0.0/16"
      ]
    },
    "subnets": [
      {
        "name": "subnetA",
        "properties": {
          "addressPrefix": "10.0.1.0/24"
        }
      },
      {
        "name": "subnetB",
        "properties": {
          "addressPrefix": "10.0.2.0/24"
        }
      }
    ]
  }
}
# Your code here

Hint

Add the second subnet object inside the subnets array after subnetA.

4

Complete the VNet configuration

Ensure the full Azure Virtual Network JSON includes myVNet with address space 10.0.0.0/16 and both subnets subnetA and subnetB with their correct address prefixes. This is the final complete configuration.

Azure

{
  "type": "Microsoft.Network/virtualNetworks",
  "apiVersion": "2021-05-01",
  "name": "myVNet",
  "location": "eastus",
  "properties": {
    "addressSpace": {
      "addressPrefixes": [
        "10.0.0.0/16"
      ]
    },
    "subnets": [
      {
        "name": "subnetA",
        "properties": {
          "addressPrefix": "10.0.1.0/24"
        }
      },
      {
        "name": "subnetB",
        "properties": {
          "addressPrefix": "10.0.2.0/24"
        }
      }
    ]
  }
}
# Your code here

Hint

Review the full JSON to confirm all parts are included and correctly named.

Practice

1. What is the main purpose of creating subnets within a Virtual Network (VNet) in Azure?

easy

A. To create virtual machines directly inside the VNet

B. To divide the VNet into smaller IP address ranges for better organization and security

C. To connect different VNets together automatically

D. To increase the total IP address space of the VNet

Solution

1. Step 1: Understand the role of subnets in a VNet

   Subnets split a VNet into smaller parts, each with its own IP range.

2. Step 2: Identify the purpose of subnetting

   Subnetting helps organize resources and apply security rules within the VNet.

3. Final Answer:

   To divide the VNet into smaller IP address ranges for better organization and security -> Option B

4. Quick Check:

   Subnet purpose = divide and organize IP ranges [OK]

Hint: Subnets split IP space inside a VNet for organization [OK]

Common Mistakes:

• Thinking subnets increase total IP space
• Confusing subnets with VNet peering
• Believing subnets create VMs automatically

2. Which of the following is the correct way to define a subnet within an Azure VNet using CIDR notation?

easy

A. 10.0.1.0/24

B. 10.0.0.256/24

C. 10.0.0.0/16

D. 10.0.0.0/33

Solution

1. Step 1: Review valid CIDR notation for subnets

   CIDR notation uses an IP address and a prefix length between 0 and 32 for IPv4.

2. Step 2: Check each option for validity

   10.0.0.0/16 is a VNet range, not a subnet. 10.0.1.0/24 is a valid subnet inside 10.0.0.0/16. 10.0.0.256/24 has an invalid IP (256 is out of range). 10.0.0.0/33 has an invalid prefix length (33 is too large).

3. Final Answer:

   10.0.1.0/24 -> Option A

4. Quick Check:

   Valid subnet CIDR = 10.0.1.0/24 [OK]

Hint: Subnet CIDR must have valid IP and prefix ≤ 32 [OK]

Common Mistakes:

• Using IP octets above 255
• Using prefix length greater than 32
• Confusing VNet and subnet CIDR sizes

3. Given a VNet with address space 192.168.0.0/16, which subnet CIDR block is valid and fits inside this VNet?

medium

A. 192.168.1.0/24

B. 192.169.0.0/24

C. 192.168.0.0/15

D. 10.0.0.0/24

Solution

1. Step 1: Understand the VNet address space

   The VNet covers IPs from 192.168.0.0 to 192.168.255.255 (a /16 block).

2. Step 2: Check which subnet fits inside the VNet

   192.168.1.0/24 (192.168.1.0/24) fits inside the VNet range. 192.169.0.0/24 is outside the 192.168.x.x range. 192.168.0.0/15 has a /15 prefix which is larger than the VNet's /16, so it extends outside. 10.0.0.0/24 is a different private IP range.

3. Final Answer:

   192.168.1.0/24 -> Option A

4. Quick Check:

   Subnet inside VNet range = 192.168.1.0/24 [OK]

Hint: Subnet must be fully inside VNet IP range [OK]

Common Mistakes:

• Choosing subnet outside VNet range
• Using larger prefix than VNet
• Confusing private IP ranges

4. You tried to create a subnet with CIDR 10.1.0.0/16 inside a VNet with address space 10.0.0.0/24. What is the problem?

medium

A. The subnet CIDR is invalid because it uses a private IP range

B. The subnet CIDR is too small for a subnet

C. The subnet CIDR overlaps with another subnet

D. The subnet CIDR is larger than the VNet address space and does not fit inside

Solution

1. Step 1: Compare subnet and VNet address spaces

   The VNet covers 10.0.0.0 to 10.0.0.255 (/24). The subnet 10.1.0.0/16 covers 10.1.0.0 to 10.1.255.255, which is outside the VNet range.

2. Step 2: Identify the error

   The subnet CIDR must be fully inside the VNet's address space. Here, it is larger and outside the VNet.

3. Final Answer:

   The subnet CIDR is larger than the VNet address space and does not fit inside -> Option D

4. Quick Check:

   Subnet must fit inside VNet range [OK]

Hint: Subnet CIDR must be inside VNet CIDR, not bigger [OK]

Common Mistakes:

• Ignoring subnet size vs VNet size
• Thinking private IP ranges are invalid
• Assuming overlap without checking

5. You have a VNet with address space 172.16.0.0/16. You want to create three subnets: 172.16.0.0/18, 172.16.64.0/18, and 172.16.128.0/17. Which statement is true about these subnets?

hard

A. The second subnet is outside the VNet address space

B. The third subnet overlaps with the first two subnets

C. All three subnets fit inside the VNet without overlapping

D. The subnet sizes are invalid for this VNet

Solution

1. Step 1: Analyze the VNet and subnet ranges

   The VNet covers 172.16.0.0 to 172.16.255.255 (/16). The first subnet covers 172.16.0.0 to 172.16.63.255 (/18). The second covers 172.16.64.0 to 172.16.127.255 (/18). The third covers 172.16.128.0 to 172.16.255.255 (/17).

2. Step 2: Check for overlaps

   The subnets cover distinct ranges: first 172.16.0.0-172.16.63.255, second 172.16.64.0-172.16.127.255, third 172.16.128.0-172.16.255.255. No overlaps, all fit within the VNet.

3. Final Answer:

   All three subnets fit inside the VNet without overlapping -> Option C

4. Quick Check:

   All three subnets fit without overlapping [OK]

Hint: Check subnet ranges carefully for overlaps [OK]

Common Mistakes:

• Miscalculating subnet ranges and thinking they overlap
• Confusing prefix lengths and their sizes
• Ignoring subnet boundaries