Troubleshooting Tip: SNMP Walk Not Pulling Information About Certain Interface.

FortiGate assigns a unique SNMP index to each interface for SNMP monitoring. In unlikely events that may arise from the configuration converted from another vendor or for some other reason, if two or more interfaces share the same SNMP index, SNMP tools may not be able to distinguish between them, leading to incomplete or missing data.

For instance:

config system interface
    edit "wan1"
        set vdom "root"
        set ip 192.168.2.150 255.255.255.0
        set type physical
        set explicit-web-proxy enable
        set alias "wan"
        set role wan
        set snmp-index 1 <----- Duplicate SNMP index.
    next
    edit "dmz"
        set vdom "root"
        set ip 192.168.3.1 255.255.255.0
        set type physical
        set snmp-index 1 <----- Same SNMP index as wan1.
    next
end

Result:

Solution:

To resolve this issue, assign a unique SNMP index to each interface. Modify the SNMP index of one of the conflicting interfaces as shown below:

config system interface
    edit "dmz"
        set snmp-index 2
    next
end

After applying this change, SNMP walk operations should correctly retrieve data for all interfaces.