after find out more detail.
i can see ip address for example new /29 assign to that virtualizor server..
arp list shows dynamic connected with particular mac address.. (i dont know who belong that mac address)..
the new ip /29 has not added to pool.. but they seems detect with particular mac address..
when i assign /29 to another server.. yes the mac address is indeed empty.
i still curious why..
seems the ip does not resolved with ARP because double mac address..
still no idea why