With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
rprSpanCurrentInUcastClassBEirOctets
rpr Span Current In Ucast Class B Eir Octets
1.0.8802.17.1.1.1.3.1.1.8
The number of received (PHY to MAC) classB EIR unicast octets in the current interval.
Back to IEEE-802DOT17-RPR-MIB MIB page.
IPHost Network monitor allows you to monitor rprSpanCurrentInUcastClassBEirOctets on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco optical switches right now.