With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cGgsnDefaultAggregIpMask
Cisco Ggsn Default Aggregate Ip Mask
1.3.6.1.4.1.9.9.240.1.3.4.1.3
This object specifies the net-mask pertaining to cGgsnDefaultAggregIpAddr.
Back to CISCO-GGSN-MIB MIB page.
IPHost Network monitor allows you to monitor cGgsnDefaultAggregIpMask 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.