And finally the latest response from Cisco:
“In order to use stateless address auto config (SLAAC), you need an external device that does the SLAAC auto config, because our SG300 can not do that. This auto config, can pass through our device, and the Switch itself can be auto configured via that extra device. We refer to this extra device as DHCPv6.”
So, definitely, I cannot use the SLAAC function on this switch,
Thanks anyway.