With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
pimRPSetGroupMask
pim RP Set Group Mask
1.3.6.1.3.61.1.1.6.1.2
The multicast group address mask which, when combined with pimRPSetGroupAddress, gives the group prefix for which this entry contains information about the Candidate-RP.
Back to PIM-MIB MIB page.
IPHost Network monitor allows you to monitor pimRPSetGroupMask 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.