Thank you for reaching out.
I understand you wish to know the which users are directed to which backend server in your Application Gateway.
I think you will be able to get this data via Azure Application Gateway Diagnostic logging via Access logs.
clientIP : IP of the immediate client of Application Gateway. If another proxy fronts your application gateway, this displays the IP of that fronting proxy.
serverRouted: The backend server that application gateway routes the request to.
You can enable diagnostic logging by following the documentation here.
Hope this helps! Please let me know if you have any additional questions. Thank you!
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