With IPHost Network Monitor you can run simple snmp requests against a Fortinet device in your network.
fgManIfMask
fg Man If Mask
1.3.6.1.4.1.12356.101.6.2.2
Mask of subnet the interface belongs to
Back to FORTINET-FORTIGATE-MIB MIB page.
IPHost Network monitor allows you to monitor fgManIfMask on Fortinet device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Fortinet switches right now.