With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cnatInterfacePktsIn
cnat Interface Packets In
1.3.6.1.4.1.9.10.77.1.3.3.1.1
Number of packets received on this interface that were translated.
Back to CISCO-IETF-NAT-MIB MIB page.
IPHost Network monitor allows you to monitor cnatInterfacePktsIn on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco routers right now.