2.1. Virtual Networks and IP Addressing

Every resource you deploy in Azure needs a network identity—an IP address within a Virtual Network. Get this foundation wrong, and you'll spend months untangling overlapping address spaces and redesigning architectures. Get it right, and everything else—peering, VPN, hybrid connectivity—falls into place.

💡 First Principle: IP address planning is permanent infrastructure. Unlike most Azure resources, you cannot easily change a VNet's address space after deployment without significant disruption. Plan for 5-10 years of growth, not just current needs.

What breaks without proper planning: Overlapping address spaces prevent VNet peering. Running out of IP addresses forces architecture redesigns. Non-contiguous addresses complicate routing and security rules.

Think of IP addressing like city planning. You wouldn't build a city without planning for roads, utilities, and future growth. A VNet address space is your city's master plan—get it wrong, and you'll spend years working around the mistakes. Consider this scenario: you deploy a hub VNet with 10.0.0.0/24, then realize you need to peer with an acquired company using the same range. Without overlapping, peering just works. With overlapping? You're rebuilding from scratch.