In the load balancing mode, which of the following regarding the statement about the processing method of hot backup by RADIUS/Portal server is correct?

In the load balancing mode, which of the following regarding the statement about the processing method of hot backup by RADIUS/Portal server is correct?
A . Account and authenty the NAS-IP-Address and accounting session-id filled in the backup packet
B. The srcip in the Radius packet sent by the AC needs to be the same, and the COA/DM device address configured in the Radius server can be different from one to the other
C. In the case of DOWN/uplink interruption of the original master node, the COA/DM message received by the node needs to be processed and synchronized to the opposite end, and the master device needs to issue authorization information to the AP
D. When the original master node, not the whole machine down/uplink is interrupted, the backup node also configures a Loopback interface with the same IP as the master node. This interface is not directly added to the IGP, but imported through import direct

Answer: A