By default nmap considers any device that responds to ARP to be "up". If you happen to be WFH, say due to a global pandemic, and on VPN, the VPN client might respond to every ARP request making it look like EVERY IP is up.
You can disable that with --disable-arp-ping, which if you Zenmap, you can add to all the profiles by editing the text file mentioned above.
Nmap's default host discovery behavior involves two ICMP requests and tcp to port 80 and 443. You can use -sn to make it just do an ICMP ping instead.
nmap -oG -
The option is actually
-oG FILENAME but the second
- makes it output to stdout.
My Most Used Options
nmap -oG - -PE -sn TARGET
-oG -= grepable format to stdout
-PE= ICMP ping
-sn= No port scan
On Windows, Profiles are in C:\Users\USERNAME\.zenmap\scan_profile.usp You need this if you want to do something like adding --disable-arp-ping to EVERY profile.