How to find Free IP address in a sub range?
Solution 1:
With nmap you can scan range in a sub-net with this syntax (i.e to scan 192.168.0.1 to 192.168.1.30 only) :
nmap 192.168.0.1-30
So you should easily be able to adapt it with your command :
nmap -v -sn -n 192.168.1.55-65 -oG - | awk '/Status: Down/{print $2}'