What's the difference? aka.ms/Azure/LoadBalancers

In Azure or on-premises, there are many different types of load balancers to use. While the basic concept is the same, they all do things slightly differently. In this post I am to help all of us determine if when and why I would use any of the possibilities that are out there. You have three options built right into Azure plus many of your favorite load balancers out there in the Azure Marketplace. We'll focus only on what you can get without going shopping to the Marketplace.

Let's start with the big picture of the three options first. For traffic manager, which is geographic load balancing for endpoints, I am just going to provide a couple of resources for you.

  1. Overview of Traffic Manager - aka.ms/Azure/Traffic
  2. Channel 9 - How Traffic Manager Works

Following the big picture below, I want to focus on comparing and contrasting Azure Load Balancer (level 4) versus Application Gateway (level 7) load balancers.

Azure Load Balancers

Comparison of Azure Load Balancer and App Gateway



App GW


Transport Layer 4

Application Level 7

Application Protocols Supported



IP Reservation


Not Supported


Virtual Machines and Cloud Services role instances

Any Azure Internal or Public IP Address

SSL Offloading

Not supported


Scale up

Automatic Reconfiguration

Service Monitoring

Health Probes

Health Probes

Distribution Mode

Hash Based or Source

Round Robin & Path Pattern

Application Support

Internal/External facing

Internal/External facing

Port Forwarding

Map internal/external ports



On all Outbound Internet traffic


Source for table Load Balancer Differences

Recently the Azure Application Gateway also just announced its Web Application Firewall (WAF). The "Overview" section discusses the OWASP top 10 web vulnerabilities that are protected by this functionality.