I have a list of about 20000 hostnames and I need to check which ones are up. I would say 98% of them are down. I have already tried powershell and python scripts without much success (couldn't set a decent timeout in each). I'm trying to use NMap with the following command:
nmap.exe -iL hostnames.txt -sn --host-timeout=200ms -oN results.txt
Even then, each down host takes about 8 seconds because NMap gets stuck trying to resolve the hostname into an IP address. Also, I see a warning at the start that says NMap couldn't import all necessary NPCap functions but i don't know if that is responsible.
Am I doing something wrong? Any suggestion?