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