This section describes the definition and purpose of IP-Link.
IP-Link enables the FW to regularly send probe packets to a specific destination IP address and determines whether faults occur based on the reply packets.
After the FW does not receive any response packet within three probe intervals (15s by default) after sending three probe packets, the FW considers the current link to be faulty, and the IP-Link status is Down. The FW performs operations for the IP-Link Down event, such as the active/standby switchover of hot standby.
After the link recovers from the fault, the FW considers that the link fault is cleared only after it receives three consecutive response packets. Then the IP-Link status becomes Up. That is, the IP-Link status does not immediately become Up after the link fault is rectified. Instead, it becomes Up after three probe intervals (15s by default).
IP-Link, automatic service link reachability detection, detects the status of the links indirectly connected to the FW to ensure service continuity.