We are trying to host multiple sites at the backend of Azure Firewall, however we have about 30 different sites and each with their own test\dev and UAT site, which means 30 x 4 and 120 sites, each one is hosted on port 443, all have their own public IP, and are configured with a DNAT rule for directing the traffic based on the source to the correct backend, we have considered a Azure Application Gateway, with host header redirect, but we haven't had a chance to implement it yet, I was wondering is there a way to be cleverer and use Azure firewall with less public IP's and route to various backends, also the prod public sites have no source specified as they're open to the public.
Hope I've explained that clearly. Thanks
• Yes, what you are trying to achieve is very much possible by creating backend pools of websites according to their purpose, common domain name or the URL path routing. For this purpose, you can use the Azure application gateway efficiently by configuring it with the required features given in it.
First, you can define wildcard hostnames in multiple site listeners for up to 5 hostnames per listener, i.e., suppose you have three domain names under which the multiple various web sites are hosted, then you can create pools of public IP addresses under that respective domain name and ensure that the request for that domain’s website is routed accordingly in application gateway. Similarly, you can host multiple subdomains of the same parent domain on the same application gateway deployment.
For more information on configuring the above, kindly refer to the documentation link below: -
• Also, you can distinguish the requests to each one of the websites with a public IP address by configuring URL based path routing rules for either each one of them or categorizing them into pools of common domain name, common URL path, content to be fetched, common purpose or any such characteristic through which you can make a collection of them. URL Path Based Routing allows you to route traffic to back-end server pools based on URL Paths of the request. One of the scenarios is to route requests for different content types to different backend server pools. Thus, in this way, you can route requests to backend website pools by defining the correct required parametric configurations.
For more information on configuring the above, kindly refer to the documentation link below: -
https://learn.microsoft.com/en-us/azure/application-gateway/url-route-overview\
Also, you can configure request routing rules based on combining the above two features in one. For more information regarding this, kindly refer to the documentation link below which describes in detail when and how you should configure the various path based and listener-based rules in application gateway: -
https://learn.microsoft.com/en-us/azure/application-gateway/configuration-request-routing-rules