Scanning logic

Scanning logic

Can you explain the logic of domain scan?
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At this moment I have following situation:I look at history tab and in "Workstation Scan History" section see that this workstation was changed several time(software and hardware). After investigation I think that is result of changing IP address. Is it true?
What if all of our workstation received ip by DHCP? Will the history tab is useless in this case?