With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
natAddrBindGlobalAddr
nat Addr Bind Global Addr
1.3.6.1.2.1.123.1.6.1.4
This object represents the public-realm network layer address that maps to the private-realm network layer address represented by natAddrBindLocalAddr. The type of this address is determined by the value of the natAddrBindGlobalAddrType object.
Back to NAT-MIB MIB page.
IPHost Network monitor allows you to monitor natAddrBindGlobalAddr 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.