If I put "external" interface on SmartOS installation to "dhcp" , it creates NEW MAC address for vnic and it gets new external IP every time.

if I put fixed UP address for external,then it does not assign it to external vnic interface

I suppose that external vnic, being on separate LAN adapter now, is supposed to serve external services from outside the internet. So how am I supposed to make that work, if it's MAC address changes every time it reboots and I can't set fixed IP address for external ?