Discovery failing to set DNS Domain values on some CI records

Review the Discovery scan for your target CI and look for the input record on the DNS ECC Queue input payload, to see if the name was resolved. This happens when the reverse DNS lookup for a CI fails. 

The input payload would show something like this: 
<result ip_address="x.x.x.x" result="unresolved"> 
<name/> 
</result> 

For a successful reverse DNS lookup, the DNS input ECC Queue record has a domain name available, as the name was successfully resolved from the IP address. 

Here is an example snippet: 
<result ip_address="x.x.x.x" result="resolved"> 
<name>ABCD</name> 
</result> 

Notice the difference in the result value for the two snippets. The unsuccessful one is 'unresolved', and the successful one is 'resolved'.

In the above example snippets, the reason the DNS Domain is not populated for the CI is that the reverse DNS lookup fails for this CI. For this, it is recommend to check with your internal teams managing your CIs or reviewing your CI for why the reverse DNS lookup is failing.