Technical Tip: OIDs to monitor Link Monitor state and statistics via SNMP

Link Monitor and SNMP (Simple Network Management Protocol) are powerful tools in network management, especially when combined.

From the SNMP server, it is possible to check the status of the Link Monitor configured on the FortiGate.

It is good to know which uplinks are up and down and notify the state of the monitored link without logging the firewall and executing the command ' diagnose sys link-monitor status'.

Here are the most common OIDs used for the Link Monitor. There are usually multiple entries - one per configured Link Monitor:

fgLinkMonitorName -  1.3.6.1.4.1.12356.101.4.8.2.1.2
Provides the name for each link-monitor.

fgLinkMonitorState -  1.3.6.1.4.1.12356.101.4.8.2.1.3

Either 1 or 0. 1 is dead, 0 is alive. 

fgLinkMonitorLatency -  1.3.6.1.4.1.12356.101.4.8.2.1.4
Average latency of the connection. 

fgLinkMonitorJitter -  1.3.6.1.4.1.12356.101.4.8.2.1.5
Average jitter seen on the connection

fgLinkMonitorPacketSend -  1.3.6.1.4.1.12356.101.4.8.2.1.6

How many packets were sent since the link-monitor was configured.

fgLinkMonitorPacketRecv -  1.3.6.1.4.1.12356.101.4.8.2.1.7

How many packets were received since the link-monitor was configured.

fgLinkMonitorPacketLoss -  1.3.6.1.4.1.12356.101.4.8.2.1.8

How many packets were lost since the link-monitor was configured.

fgLinkMonitorVdom - 1.3.6.1.4.1.12356.101.4.8.2.1.9

Virtual domain the link monitor entry exists in.

fgLinkMonitorBandwidthIn - 1.3.6.1.4.1.12356.101.4.8.2.1.10

The available bandwidth in Mbps of incoming traffic detected by a link monitor on its interface.

fgLinkMonitorBandwidthOut - 1.3.6.1.4.1.12356.101.4.8.2.1.11

The available bandwidth in Mbps of outgoing traffic detected by a link monitor on its interface.

fgLinkMonitorBandwidthBi - 1.3.6.1.4.1.12356.101.4.8.2.1.12

The available bandwidth in Mbps of bi-direction traffic detected by a link monitor on its interface.

fgLinkMonitorOutofSeq - 1.3.6.1.4.1.12356.101.4.8.2.1.13

The total number of out of sequence packets received.

fgLinkMonitorServer -  1.3.6.1.4.1.12356.101.4.8.2.1.14
Destination server of the link-monitor

fgLinkMonitorProtocol - 1.3.6.1.4.1.12356.101.4.8.2.1.15

Link Monitor protocol.

Here is an example of what can be seen when querying these OIDs:

To monitor SD-WAN Health Checks, refer to Using SNMP to monitor health check | FortiGate / FortiOS 7.4.8 | Fortinet Document Library.