With IPHost Network Monitor you can run simple snmp requests against a Fortinet device in your network.
fgVpnTunEntRemGwyPort
fg Vpn Tunnel Ent Remote Gwy Port
1.3.6.1.4.1.12356.101.12.2.2.1.5
port of remote gateway used by tunnel, if UDP
Back to FORTINET-FORTIGATE-MIB MIB page.
IPHost Network monitor allows you to monitor fgVpnTunEntRemGwyPort on Fortinet device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Fortinet access points right now.