With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cdxCpeToCmTable
Cisco DOCSIS Cpe To Cable Modem Table
1.3.6.1.4.1.9.9.116.1.3.9
This table contains information about cable modems with CPE connects to. It is not intended to walk the whole table. An application would need to query this table base on the specific index. Otherwise, it will impact the CMTS performance due to the huge size of this table. The agent creates/destroys/modifies an entry whenever there is update for the cable modem that CPE connects to.
Back to CISCO-DOCS-EXT-MIB MIB page.
IPHost Network monitor allows you to monitor cdxCpeToCmTable on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco multiplexers right now.