With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
netDefaultGateway
net Default Gateway
1.3.6.1.4.1.52.4.12.30.1.10.2
The IP Address of the default gateway. If this value is undefined or unknown, it shall have the value 0.0.0.0.
Back to RMON2-MIB MIB page.
IPHost Network monitor allows you to monitor netDefaultGateway 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.