My company wants something like the Application Gateway to be a scalable entrypoint of all incoming requests, with SSL offloading, and balance those requests to external web servers, which are not on our Azure subscription, but belong to the company.
If Application Gateway is indeed the recommended way, how can I declare in the XML configuration file something like that? And if it's not, what's the best way I can achieve that?
application gateway is an option to achive this but by using an application gateway you use an AzureVM ressource. The scalability is ok but we have to pre-create more application gateways in case of a scale out. For a scale down you should also check first how to reroute traffic from the current gateway to the others before you scale down. i would reccomend an another design. by using azure app-services. this is a webserver farm as a service. in the webserver is IIS running and you can create a forward / redirect reverse proxy or ARR. check out point like azure topics like Application request routing and reverse proxy:
http://blogs.iis.net/carlosag/setting-up-a-reverse-proxy-using-iis-url-rewrite-and-arr
http://www.iis.net/learn/extensions/url-rewrite-module/iis-url-rewriting-and-aspnet-routing
regards
patrick