Do not configure a Rendezvous Point (RP) or Bootstrap Router (BSR) on the vIST VLAN because you cannot ping them outside of the vIST VLAN subnet. When you enter the ip pim enable command on the vIST VLAN, the following message displays:
WARNING: Please do not use virtual IST VLAN IP address for BSR and RP related configurations, as unicast packets to virtual IST vlan IP address from outside of virtual IST vlan subnet will be dropped. Use Loopback or CLIP interface IP address for BSR and RP related configurations.