With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
ceeSubInterfaceCount
Cisco Ethernet-like Sub Interface Count
1.3.6.1.4.1.9.9.645.1.2.1.1.1
This object represents the number of subinterfaces created on a Ethernet-like interface.
Back to CISCO-ETHERLIKE-EXT-MIB MIB page.
IPHost Network monitor allows you to monitor ceeSubInterfaceCount on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco wireless switches right now.