With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
rprSpanCurrentOutMcastClassCOctets
rpr Span Current Out Mcast Class C Octets
1.0.8802.17.1.1.1.3.1.1.34
The number of transmitted (MAC to PHY) classC multicast and broadcast octets in the current interval.
Back to IEEE-802DOT17-RPR-MIB MIB page.
IPHost Network monitor allows you to monitor rprSpanCurrentOutMcastClassCOctets on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco firewalls right now.