With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cseMetAllocatedSpcFreeEntries
CISCO SWITCH ENGINE Met Allocated Spc Free Entries
1.3.6.1.4.1.9.9.97.1.10.1.1.4
The number of free entries reside in allocated space of this MET.
Back to CISCO-SWITCH-ENGINE-MIB MIB page.
IPHost Network monitor allows you to monitor cseMetAllocatedSpcFreeEntries 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.