With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cfmGenInfoInuseFgids
Cisco Fabric Multicast Gen Info Inuse Fgids
1.3.6.1.4.1.9.9.255.1.1.2
The current number of FGIDs that are currently in use by the managed system.
Back to CISCO-FABRIC-MCAST-MIB MIB page.
IPHost Network monitor allows you to monitor cfmGenInfoInuseFgids on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco wireless switches right now.