You need to collect accounting information from your VPN solution and decide to deploy and configure Microsoft Defender for Identity. 
You use a Microsoft Routing and Remote Access Server as a VPN server. 
You want Defender for Identity to integrate with your VPN solution by listening to RADIUS accounting events forwarded to the Defender for Identity sensors. 
 You install the Microsoft Defender for Identity Standalone sensor on your RRAS server. 
Next you open UDP port 1813 your Defender for Identity standalone sensors to enable VPN integration. 
What should you do next to configure RADIUS Accounting on the VPN system?

Answer options:

A.Set the SSL Certificate Binding to use HTTP.
B.Configure an Accounting provider.
C.Configure a IPv6 static IP address.
D.Allow custom IPsec policy for L2TP/IKEv2 connections.

Correct Answer: B 
You must configure the Accounting provider and set it to RADIUS Accounting. 
By enabling Radius Accounting, the Defender for Identity sensor will enable a pre-provisioned Windows firewall policy called Microsoft Defender for Identity Sensor to allow incoming RADIUS Accounting on port UDP 1813. See exhibit: 

Option A is incorrect. Binding the SSL Certificate to use HTTP is not a prerequisite to integrate Defender for Identity with your VPN server in this scenario.
Option C is incorrect. Configuring a static IPv6 address is not a prerequisite to integrate Defender for Identity with your VPN server.
Option D is incorrect. Use this feature to define a preshared key. This is not a prerequisite to integrate Defender for Identity with your VPN server in this scenario.
Reference: 
To know more about integrating Defender for Identity with VPN, please refer to the link below: 

https://docs.microsoft.com/en-us/defender-for-identity/install-step6-vpn