This function of L2 BNG allows you to cut off traffic from Internet to the subscriber if the subscriber is not active (there is no traffic from the subscriber). While operating, for each subscriber L2 BRAS memorizes the arrival time (T) of the last packet from the subscriber. During the T + time interval, the subscriber’s activity is considered to be active. All packets from inet to the subscriber are passed through. If the subscriber is inactive (the activity interval has been exceeded since the last packet from the subscriber) L2 BRAS drops the packet.
Additionally, you can set the subscriber ping function if the subscriber has become inactive. Ping is carried out by sending an ARP packet to the subscriber: if there is a response to such request, the time of the last packet arrival from the subscriber will be updated meaning the subscriber is considered active.

It is used only in case of inbound traffic (from WAN to LAN). Activity monitoring is especially relevant for subscribers with a static white address.

Subscriber activity control is configured by the following parameters in fastdpi.conf:

• bras_subs_activity_timeout - sets the activity interval in seconds, 0 (default value) - disables activity monitoring
• bras_subs_activity_ping_timeout - sets timeout of pinging the subscriber with an ARP request in seconds, 0 (default value) - disables ARP ping. If the subscriber is inactive, ARP requests will be sent everybras_subs_activity_ping_timeout seconds.