What is Azure Application Gateway?

Azure Application Gateway is a web traffic (OSI layer 7) load balancer that enables you to manage traffic to your web applications. Traditional load balancers operate at the transport layer (OSI layer 4 - TCP and UDP) and route traffic based on source IP address and port, to a destination IP address and port.

Application Gateway can make routing decisions based on additional attributes of an HTTP request, for example URI path or host headers. For example, you can route traffic based on the incoming URL. So if /images is in the incoming URL, you can route traffic to a specific set of servers (known as a pool) configured for images. If /video is in the URL, that traffic is routed to another pool that's optimized for videos.

This type of routing is known as application layer (OSI layer 7) load balancing. Azure Application Gateway can do URL-based routing and more.

Note

Azure provides a suite of fully managed load-balancing solutions for your scenarios. If you need high-performance, low-latency, Layer-4 load balancing, see What is Azure Load Balancer? If you're looking for global DNS load balancing, see What is Traffic Manager? Your end-to-end scenarios may benefit from combining these solutions.

For an Azure load-balancing options comparison, see Overview of load-balancing options in Azure.

Features

To learn about Application Gateway features, see Azure Application Gateway features.

Gateway 1: Maximum of 10 instances. Uses a private frontend IP configuration

What does the instance mean? does eahc instance require a private forntend IP?

Gateway 1:
- It refers to an Azure Application Gateway.
- It allows up to 10 instances (backend servers) to be load balanced.
- These instances can be virtual machines, VM scale sets, or other resources.
- The gateway distributes incoming traffic among these instances.
Private Frontend IP Configuration:
- Each instance does not require a separate private frontend IP.
- Instead, the gateway itself has a private frontend IP.
- All instances share this common private IP for incoming traffic.
- This IP is used for communication within the virtual network.

In summary, the instances represent the backend servers, and the private frontend IP is associated with the entire gateway, not each individual instance.