With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
vsanNumber
vsan Number
1.3.6.1.4.1.9.9.282.1.1.1
The number of VSANs configured on this device.
Back to CISCO-VSAN-MIB MIB page.
IPHost Network monitor allows you to monitor vsanNumber 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.