Using next_available_ip WAPI call, how does NIOS determine if IP address is available for handout?

[#1]

To determine if an IP address is available for handout when using the next_available_ip WAPI call, does NIOS include a ping of the IP address as one of the criteria? In other words, if an IP address is pingable but is not configured in a Host (or A or PTR) record, is it eligible for handout when using the next_available_ip address WAPI call? I've searched for the criteria used but have not found an answer. I don't have an easy way to test. Thanks.

[#2]

GM in many cases won't have l3 access to the most of the IPs, so I doubt it does any ping checks. Most likely checks for any A or HOST records.