Do I need LDAP as a Data Resource to run scans by host name?
I use to run my scans by IP but have switched to using hostnames as targets. When I run a scan on close to 500 systems the reports come back with only 175 systems.
No. You can scan by hostname without an LDAP connection.
Sounds like something else funky is going on..possibly with DNS.
try flushing your DNS and arp caches on the scanner...not sure this well help but worth trying.
Also check your dns suffixes on your active scanner NIC-be sure to list all.
What does the LDAP interface buy you then?
You can use it to import hosts for scanning-useful if you would like to scan an entire OU.