With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cagwInstanceTable
Cisco's ASN Gateway Instance Table
1.3.6.1.4.1.9.9.638.1.1.1
The ASN-GW Instance Table contains an entry for each physical ASN Gateway.
Back to CISCO-ASN-GATEWAY-MIB MIB page.
IPHost Network monitor allows you to monitor cagwInstanceTable 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.