Like your layer 7 load balancer in your traditional datacenter, Azure application gateway takes care of your HTTP/HTTPS based requests. It works at application layer (level 7 of OSI model) and works as a reverse-proxy as well. In application gateway, client connections are terminated at gateway and then forwarded to application.

Let me show, how to create and configure application gateway step-by-step.

Login to the Azure Portal and select “+ Create a resource”. Select the “Networking” and then select “Application Gateway”.

In the basic configuration settings:

Enter the name of the application gateway. Always use a name for any components in Azure that fit for purpose and easy to distinguish.

Select the application gateway tier:

• Standard: As any other layer 7 load balancer, it provides HTTP(S) load balancing, cookie-based session affinity, secure sockets layer (SSL) offload, end-to-end SSL, URL based content routing, multi-site routing, websocket support, health monitoring, SSL policy and ciphers, request redirect, and multi-tenant back-end support etc.
• WAF: WAF is an advanced version of standard application gateway with application firewall capabilities that supports all standard AG features along with protection of web applications from common web vulnerabilities and exploits. Application gateway WAF comes pre-configured with OWASP (online web application security project) modsecurity core rule set (3.0 or 2.29) that provides baseline security against many of these vulnerabilities. It provides protection against SQL injection, cross site scripting, command injection, HTTP request smuggling, HTTP response splitting, remote file inclusion attack, HTTP protocol violations and anomalies, bots, crawlers, scanners, application misconfiguration and HTTP Denial of Service etc.

Select SKU size based on your requirement. AG sku comes in small, medium and large size.

Select instance count based on your need. The default instant count is 2.

Select subscription, resource group and location.

Once completed all basic configuration settings, click on OK.

In settings panel, complete following application gateway specific configuration settings:

Select virtual network and subnet that is going to associate with this application gateway.

Complete frontend IP configuration based on your application gateway requirements.

Set idle timeout settings and set the DNS name label.

Select the listener configuration protocol and associated port number.

Once completed with the configuration details, click on OK.

If you select HTTPS in listener configuration, upload PFX certificate file and provide credentials. Once completed with the configuration, click on OK.

Review the summary of the configuration and click on OK to create application gateway.

In the overview section, review the basic configuration.

In configuration panel under settings, you can change the application gateway tier, SKU size and instant count based on your requirements.

In Web application firewall panel under settings, you can upgrade to WAF tier if using standard tier and can also “enable/disable” firewall, configure firewall mode “detection/prevention”, configure rule set with OWASP and advanced configuration for your application gateway.

In Backend pools panel under settings, add and configure backend pools for application gateway. Click on add or existing backend pool to define the backend pool settings.

Click on “+ Add target” to define targets either using “IP address or FQDN” or “Virtual machine”. Click on rules to configure redirection if required.

In HTTP settings under settings, add or edit backend HTTP(S) settings such as cookie based affinity, request timeout, protocol and port etc.

In frontend IP configurations panel under settings, review IP configurations, type, status and associated listeners.

In listeners panel under settings, add basic and multi-site listeners.

In rules panel under settings, define basic and path-based rules based on your requirements.

In health probes panel under settings, you can add and edit health probes.

Once you add health probe, you define following parameters:

Name of the health probe.

Protocol either HTTP or HTTPS.

Enter the host name, path, interval in seconds, timeout in seconds and number of unhealthy thresholds.

In the properties section, you can look at the application gateway properties.

Under the locks section, you can create and configure the lock type to prevent changes and protecting the application gateway profile.

Under the “Automation script” download the script or add to library for reuse.

In the metrics panel, you can monitor the metrics of the application gateway by following parameters:

• Current Connections
• Failed Requests
• Healthy Host Count
• Response Status
• Throughput
• Total Requests
• Unhealthy Host Count

In alert rules panel under settings, you can define conditional rules.

In diagnostics logs panel under settings, you can view the logs of the resources.

In backend health under settings, you can review the status of the backend pool.

I hope, this article helped you to understand, create, configure and manage Azure application gateways.