D-Link DIR-840 User Manual page 34

Section 3 - Setup
Maximum Idle
Enter a maximum idle time during which the Internet
Time: connection is maintained during inactivity. To disable this
feature, enable Auto-reconnect.
DNS Addresses:
Enter the Primary and Secondary DNS Server Addresses
(Static PPPoE only).
Keep Alive: To keep prevent inactivity from assuming a dropped
connection you can Use LCP Echo Request to request
frequent pings to maintain communication. This is disabled
by default.
D-Link DIR-840 User Manual 30