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Microsoft Azure · Networking & Containers

Networking Fundamentals

You don’t need to be a network engineer to use the cloud — but a few core ideas make VNets, firewalls and load balancers much easier to understand.

Intermediate 5 min Lesson 17 of 28
Before you start:Azure Fundamentals
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On this page · 5 min · Intermediate

On this page

  1. Learning objectives
  2. Explanation
  3. Code example
  4. Step by step
  5. Real-world use
  6. Common mistakes
  7. Best practices
  8. Remember this
  9. Practice exercise
  10. Mini quiz
  11. Related topics
  12. My notes
Reading time
5 min
Difficulty
Intermediate
Updated
Oct 29, 2026

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Interview questions

Learning objectives#

  • Read CIDR notation
  • Explain subnets and private IP ranges
  • Describe how DNS works
  • Compare Azure load balancing options

Explanation#

An IP address identifies a machine. Private ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are used inside networks and are not reachable from the internet.

CIDR notation describes a range: /16 fixes the first 16 bits, leaving 65,536 addresses; /24 leaves 256. Azure reserves 5 addresses in every subnet, so a /24 subnet has 251 usable addresses.

DNS translates names (api.techiebabaji.com) into IP addresses. Azure DNS hosts public zones; private DNS zones resolve names inside VNets.

Load balancing in Azure: Load Balancer (layer 4, TCP/UDP), Application Gateway (layer 7 HTTP with a web application firewall) and Front Door (global HTTP entry point with CDN and WAF).

Code example: Planning a VNet address space#

TextPlanning a VNet address space Illustrative
VNet         10.0.0.0/16     65,536 addresses
├─ web       10.0.1.0/24       251 usable (Azure reserves 5)
├─ api       10.0.2.0/24       251 usable
├─ data      10.0.3.0/24       251 usable
└─ (spare)   10.0.4.0 – 10.0.255.255 for future subnets
Expected output
Each tier gets its own subnet, so traffic between tiers can be controlled with network security groups.

This example is illustrative. Copy or download it and run it in your own environment; the expected output is shown above.

Step-by-step explanation#

  1. /16 gives room for many subnets.
  2. Each /24 subnet holds one tier of the application.
  3. Leaving spare space avoids painful re-addressing later.
  4. The ranges must not overlap with on-premises or other VNets you will connect.

Real-world use case#

Before creating any VNet, teams agree an IP plan so networks can later be peered or connected to the office VPN without conflicts.

Common mistakes#

Overlapping address spaces

Two VNets that both use 10.0.0.0/16 cannot be peered. Plan unique ranges.

Subnets that are too small

Some services need dedicated, larger subnets. Leave headroom.

Best practices#

  • Plan IP ranges before building
  • Use private ranges and avoid overlaps
  • Separate tiers into subnets
  • Use Front Door or Application Gateway for public HTTP traffic

Remember this#

Smaller /number = bigger network (/16 > /24).

Azure keeps 5 addresses per subnet.

L4 = Load Balancer, L7 = Application Gateway, Global = Front Door.

Practice exercise#

Your task: How many addresses does a /26 subnet contain, and how many are usable in Azure?

Show solution
Text Illustrative
/26 → 2^(32-26) = 64 addresses; 64 − 5 reserved = 59 usable.

Mini quiz#

Networking Fundamentals quizMultiple choice Question 1 of 1

Which Azure service is a layer-7 HTTP load balancer with a web application firewall?

Score so far: 0/0

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My notes#

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