With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cnatSessionTransPublicPort
cnat Session Trans Public Port
1.3.6.1.4.1.9.10.77.1.2.5.1.13
The translated transport port of the session endpoint that belongs to the public network. The value of this object is equal to that of the original transport port (cnatSessionOrigPublicPort) when there is no translation.
Back to CISCO-IETF-NAT-MIB MIB page.
IPHost Network monitor allows you to monitor cnatSessionTransPublicPort 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.