Introduction to Azure Application Gateway

Azure Application Gateway is a web traffic load balancer that enables you to manage traffic to your web applications. It offers load balancing, a Web Application Firewall (WAF), and a web application accelerator.

What is Azure Application Gateway?

Application Gateway provides routing capabilities based on attributes of the request, such as the URI path or host headers. It supports multiple load balancing strategies to distribute incoming traffic across multiple backend servers, ensuring high availability and scalability for your applications.

Key Capabilities

Load Balancing: Distributes incoming HTTP(S) traffic across multiple backend instances.
Web Application Firewall (WAF): Protects your web applications from common web vulnerabilities and exploits.
SSL Termination: Offloads SSL decryption from your web servers, simplifying management and improving performance.
Cookie-based Session Affinity: Ensures that requests from a particular client are sent to the same backend server.
URL-based Content Routing: Routes requests to different backend pools based on the requested URL.
Host-based Routing: Routes requests to different backend pools based on the host header in the request.
Health Probes: Monitors the health of backend instances and routes traffic only to healthy servers.

When to Use Application Gateway

Application Gateway is ideal for scenarios where you need to:

Load balance HTTP(S) traffic across multiple backend servers.
Provide a secure entry point to your web applications.
Offload SSL decryption.
Implement advanced routing rules based on URLs or host headers.
Protect your applications from common web attacks with a WAF.

Application Gateway Tiers

Application Gateway offers different tiers to meet varying performance and feature requirements:

Standard v2: Offers autoscaling, zone redundancy, and performance improvements.
WAF v2: Includes all features of Standard v2 plus a Web Application Firewall for enhanced security.

Tip: For new deployments, it is recommended to use the v2 SKU, which offers enhanced features like autoscaling and zone redundancy.

Core Components

Understanding the core components of Application Gateway is crucial for effective configuration:

Frontend IP configuration: The IP address(es) that the Application Gateway listens on.
Listeners: A combination of frontend IP, port, and protocol that listens for incoming requests.
Rules: Defines how requests are routed to backend pools.
Backend pools: Groups of backend servers that receive traffic.
HTTP settings: Defines settings for requests sent to the backend pool, such as protocol, port, and cookie-based affinity.
Health probes: Used to monitor the health of backend servers.

This document provides a foundational understanding of Azure Application Gateway. For detailed configuration and advanced scenarios, please refer to the subsequent sections of this documentation.