With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cIsnsNumPortals
Cisco iSNS Num Portals
1.3.6.1.4.1.9.10.116.1.1.2.1.4
The current total number of Portals registered in iSNS. This is the number of rows in cIsnsRegPortalTable.
Back to CISCO-IETF-ISNS-MGMT-MIB MIB page.
IPHost Network monitor allows you to monitor cIsnsNumPortals 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.