Проверьте FreeRadius. net Код здесь
//args = new string[4];
//args[0] = "192.168.1.1";
//args[1] = "secret";
//args[2] = "username";
//args[3] = "password";
RadiusClient rc = new RadiusClient(args[0], args[1]);
// Use username/password here
RadiusPacket authPacket = rc.Authenticate(args[2], args[3]);
authPacket.SetAttribute(new VendorSpecificAttribute(10135, 1, UTF8Encoding.UTF8.GetBytes("Testing")));
authPacket.SetAttribute(new VendorSpecificAttribute(10135, 2, new[] { (byte)7 }));
RadiusPacket receivedPacket = await rc.SendAndReceivePacket(authPacket);