Day-5 | Azure Virtual Network(VNet) Explained | Beginner Level ✔️

Day 5: Azure Virtual Network (VNet) Explained (Beginner)

Overview

This video is Day 5 of the “Azure Zero to Hero” series (presenter: Abishek). It covers the basics and motivation for Azure Virtual Network (VNet), explains related networking primitives, and maps them to real‑world use cases.

Key concepts and why VNets exist

• Problem: without logical network isolation, customer VMs could share the same physical host/network and create security and tenant‑isolation risks.
• Solution: Azure Virtual Network (VNet) provides logical isolation of networking within Azure’s physical infrastructure (equivalent to AWS VPC).
• You can create multiple VNets per subscription/organization as needed.

Without logical network isolation, customer VMs could share the same physical host/network and create security/tenant‑isolation risks. VNets provide the logical isolation layer.

CIDR and VNet/subnet sizing

• VNet and subnet sizes are defined using CIDR notation (example: 10.0.0.0/16 → 65,536 IP addresses).
• The presenter references a dedicated CIDR deep‑dive video (linked in the description) for more details on IP sizing.

Subnets and logical separation

• Best practice is to split a VNet into multiple subnets by role, for example:
  • Web (public-facing)
  • Business-logic / app (internal)
  • Database (restricted)
• Purpose: subnets allow different exposure and security requirements for each role (web facing vs internal app vs DB).

Network Security Group (NSG)

• NSGs define inbound and outbound security rules.
• NSGs can be applied to a subnet or to individual VM network interfaces.
• Example: block internet (public) access to the DB subnet and allow access only from the app subnet or specific CIDR ranges.

Application Security Group (ASG)

• ASGs let you group VMs by application role (e.g., all business‑logic instances).
• Using NSGs with ASGs enables finer‑grained policies, for example allowing only the ASG for the app tier to access the DB, even when app and web VMs share a subnet.

Default VNets/subnets

• Azure creates default VNets/subnets to simplify onboarding.
• In production, create custom VNets/subnets and configure appropriate NSG/ASG rules instead of relying on defaults.

Route tables and User‑Defined Routes (UDR)

• Route tables and UDRs control how traffic flows within a VNet/subnet.
• They allow custom next hops and routing behavior (peering, NAT, virtual appliances).
• The presenter will cover routing in more detail during the demo portion of the video.

Practical / teaching notes

• The presenter will demonstrate NSG, ASG, and routing with hands‑on configuration in a later demo.
• A GitHub repository with day‑wise notes and the full course syllabus (Day 1–Day 25) is linked in the video description.
• The CIDR deep‑dive video is also linked in the description for additional IP sizing details.

Guides / tutorials referenced

• Azure Zero to Hero series (day‑wise curriculum)
• Day 5: VNet overview (this video)
• CIDR explainer video (detailed, ~30+ minutes)
• GitHub repo with day‑wise notes and syllabus

Main speaker / source

• Abishek (channel owner / presenter)