• When compared to Azure Load Balancer this uses app layer routing as mentioned in 202404131219 External Access
• can add firewall etc

Routing

• path based routing : based on url send to different backend servers
• Multi-site routing: different web apps on the same Azure Application Gateway
  • example: contoso.com and sajal.net
• can redirect traffic
  • redirect http traffic to https for example
• can rewrite http headers
• create custom error messages

Components

• front-end ip
  • receives the request
  • only 1 public and 1 private ip
• web application firewall (optional)
  • checks for threats based on owasp
• listener
  • accepts traffics and routes to backend pools based on routing rules
• back-end pools
• health probes
  • response between 200 and 399 considered healthy
  • default probe waits for 30 sec

references:

MS Learn