5.1.2.1. Configure Public and Private IP Addresses

5.1.2.1. Configure Public and Private IP Addresses

💡 First Principle: IP addresses are the fundamental identifiers for network communication; configuring them correctly (public vs. private, static vs. dynamic) is essential for enabling controlled, secure, and reliable connectivity for all Azure resources.

Scenario: You are deploying a production web server on an Azure Virtual Machine. It needs a static public IP address for users to access it, and a static private IP address for communication with a backend database. The public IP address should be resilient to Availability Zone failures.

What It Is: IP addresses are numerical labels assigned to devices connected to a computer network.

Private IP Addresses:

• Used for internal communication within a VNet or with on-premises networks.
• Assignment: Dynamic (default) or Static (reserved).
• Use cases: Internal VMs, databases, and load balancers.

Public IP Addresses:

• Enable inbound/outbound communication with the internet.
• SKUs:
  • Basic: Retired on 30 September 2025. New Basic public IP addresses cannot be created; existing ones continue to work but are unsupported and have no SLA.
  • Standard: Zone-redundant by default, secure by default, recommended for production.
• Assignment: Static only (Standard SKU does not support dynamic allocation).
• Use cases: Public-facing web servers, load balancers, VPN gateways.

Visual: Public vs. Private IP Addresses

⚠️ Common Pitfall: Treating the Basic SKU for public IP addresses as still selectable. Basic public IPs were retired on 30 September 2025 — new ones cannot be created, and existing ones run unsupported with no SLA, so migration to Standard is the live task. Standard SKU offers critical features like Availability Zone redundancy and is secure by default (requiring explicit NSG rules for inbound traffic).

Key Trade-Offs:

• Static vs. Dynamic IP: Static IPs provide a consistent address but may incur a small cost even when unassigned. Basic-SKU dynamic IPs are released when the resource is deallocated but are not predictable; Standard-SKU addresses are always static and continue to bill while allocated.

Reflection Question: How does configuring public and private IP addresses (including dynamic vs. static, and Basic vs. Standard SKUs for public IPs) fundamentally provide controlled, secure connectivity for Azure resources, balancing accessibility and security for diverse communication needs?