With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
ipMRouteEntryCount
ip M Route Entry Count
1.3.6.1.2.1.83.1.1.7
The number of rows in the ipMRouteTable. This can be used to monitor the multicast routing table size.
Back to IPMROUTE-STD-MIB MIB page.
IPHost Network monitor allows you to monitor ipMRouteEntryCount on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco switches right now.