In MFF networking, if the gateway is used to perform accounting according to the length of time users are online, the gateway must be able to accurately record these durations. By default, the MFF-enabled device sends ARP reply packets in response to ARP request packets sent from the gateway. The MFF-enabled device can send ARP reply packets as long as the MFF entry is not aged out. As a result, the gateway considers users online even if they have gone offline.
To solve this problem, configure the MFF-enabled device to transparently transmit ARP request packets sent from the gateway to the user. Then, the MFF-enabled device does not respond to the ARP packets. If the gateway does not receive the ARP reply packet from a user, the gateway considers that the user has gone offline. This configuration allows the gateway to monitor user online/offline status and correctly perform accounting.