This article describes link health monitoring, which measures the health of links by sending probes to a server with FQDN.
Scope
FortiGate.
Solution
It is possible to use FQDN as a server under the link monitor.
config system link-monitor edit "1" set server “google.com” next
It is necessary to make sure that this FQDN can be resolved by FortiGate. Otherwise, it will not be able to create a source route and remove the static route.
Example:
config system link-monitor edit "1" set srcintf "port1" set server "google.com" "goooole123.com" next end
Here, FortiGate will not be able to resolve goooole123.com. Checking the link monitor output will show that it is unable to create a source route, which makes the link monitor ineffective.
di sys link-monitor status Link Monitor: 1, Status: alive, Server num(2), HA state: local(alive), shared(alive) Flags=0x1 init, Create time: Wed Jul 31 17:11:01 2024 Source interface: port1 (3) Interval: 500 ms Service-detect: disable Diffservcode: 000000 Class-ID: 0 Peer: google.com(142.251.41.78) Source IP(10.9.10.253) Route: 10.9.10.253->142.251.41.78/32, gwy(10.9.15.254) <- protocol: ping, state: alive Latency(Min/Max/Avg): 10.225/10.344/10.281 ms Jitter(Min/Max/Avg): 0.000/0.080/0.033 ms Packet lost: 0.000% Number of out-of-sequence packets: 0 Fail Times(0/5) Packet sent: 10, received: 10, Sequence(sent/rcvd/exp): 11/11/12 Peer: goooole123.com(0.0.0.0) <- Source IP(10.9.10.253)