I have been using InsightVM for a while now and have always had this thind of issue.
I have a server with mutilple IPs (a windows webserver), the server has the agent installed, and it is also scanned over IP and over the virtualization cluster.
The issue is that while I assume that having the agent installed will give all information to InsightVM and it will show only one asset with all the IP addresses, InsightVM doesn’t seem intelligent enough for that and I still see it as multiple assets, one per IP.
I’m sure I’m the one that don’t understand the tool (while I think it could be explained better), but could you please explain me how should I setup the scans or any other thing to correct this?
I had this issue as well (16 different IPs on a shared Web Farm)
I found that the issue was due to discovery and not enough correlating data.
The discovery without authentication cannot pull enough information about the IP to link it to the Agent.
For me, I found that doing the discovery step first, then only vuln scanning the found Assets, ended up not saving me anything on performance. I switched to just doing the full authenticated discovery and vuln scan together took the same amount of time and resolved some of the duplicate issues.
The other place that was doing this was the vCenter Discovery. vCenter discovery was giving different names to IP then showing up as duplicates.
The two separate scans was how it was designed when I tool over and logically made sense to me, but in practice the single scan was more accurate and less resource intensive and resolved my duplicate issue.
On a side note though, you might want to open a ticket with support because I heard yesterday that there might be an issue with some people and their Asset linking.