In a previous article I showed where to find SNMP MIBs for a Fortinet Fortigate firewall device. Here's how to add a new MIB to net-snmp so the toolset can use it.
FIrst, download the MIB files and copy them to /usr/share/snmp/mibs
Look at the top of the file for a line like: YOUR-MIB-NAME DEFINITIONS ::= BEGIN
"YOUR-MIB-NAME" is the name of the MIB.
/etc/snmp/snmp.local.conf) and add the line:
Full details on the net-snmp site: