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https://blog.it-kb.ru/2015/01/21/windows-server-2012-r2-remote-access-configure-l2tp-ipsec-vpn-server-in-nlb-cluster-with-two-factor-authentication-based-on-user-domain-account-and-computer-certificate-with-nps-radius-authorization/
Windows Server 2012 R2 Remote Access - Настраиваем VPN сервер с двухфакторной аутентификацией на базе L2TP/IPsec и авторизацией через RADIUS