Troubleshooting Tip: SNMP index changing on FortiSwitch

Upon FortiSwitch reboot, the SNMP index on the FortiSwitch changes, which can lead to broken monitoring if the snmp-index is being used for monitoring various links, such as the trunks between the switches.

Note that this is an expected behavior and not an issue:

• SNMP Index values are dynamically assigned during the boot process.

• The assignment depends on the order in which interfaces initialize.

• During startup, some interfaces may come up earlier than others, causing:

  • A different sequence of interface detection.

  • A shift in SNMP index values compared to the previous boot.

To avoid the behavior, monitor the interfaces with the interface name or description instead of the SNMP index value, or set a static index on the interface.

Below is an example to set the static SNMP index value from the FortiGate CLI: