Hi Roopesh - right; the IsVirtual attribute also depends on the discovery logic which initially had created the device(server) models. So in case the discovery is done via the Spectrum AutoDiscovery i.e. by using an IP-range and the Servers are responsive to this discovery (AND there was no Virtual Host Manger triggered discovery).
So in case there is no VMware Manager modeling then you will find this attribute always on "No".
Background here is the fact, that CA Spectrum can not "see" if this is a virtual machine in case it is running an SNMP-agent acting "transparent" as a standard server (which is intentionally what is should!).
So - to enable CA Spectrum to recognize which "hosts" are in context of a VMware (or other Virtualization platfrom / Hyper-V / Zones .. etc ..) - you have to start building up this VMware context first - and then to create the server modeling via the VMware/Virtual Host Manager logic - then you see the "VM"-attribute - recognized via the VMware service that these hosts are VM-hosted machines. may this helps here, cheers, Joerg