Description
This article describes why FortiOS uses 'Link Monitor' and 'Link-Monitor' for different scopes.
Scope
FortiGate.
Solution
The 'Link Monitor' is monitoring the status of every interface.
It is enabled by default, and it does not require any additional settings.
The log entry is 'action="interface-stat-change" status="DOWN" msg="Link monitor: Interface WAN2 was turned down' (or up).
'Link-monitor', instead, is a feature where FortiGate is a link health monitor that is used to determine the health of a single interface.
It is configured in the config system link-monitor.
When 'Link-Monitor' is failing, an event is registered in the FortiGate.
When 'Link-Monitor' is failing, an event is registered in the FortiGate.
Link Monitor changed state from alive to die, protocol: ping.
If the 'Link-monitor' option, like 'update-static-route' is configured, this event will pop up too.
If 'Link-monitor' is used to bring other interfaces down when the link monitor fails, a 'Link Monitor' event is registered, but as a result of 'Link monitor' failure.
To verify the link monitor status when the destination is not reachable in the CLI, the status is set to dead:
diagnose sys link-monitor status
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