With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
docsDevSerialNumber
DOCSIS Device Serial Number
1.3.6.1.2.1.69.1.1.4
The manufacturer's serial number for this device.
Back to DOCS-CABLE-DEVICE-MIB MIB page.
IPHost Network monitor allows you to monitor docsDevSerialNumber 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.