Basic threaded ICMP discovery script, written in Python 3. Should work across Windows/Linux/OSX, but haven't tested extensively. Technically, pinger can scan Class B or A ranges but I'd use a pro tool for that if I were you.
Compatible with Python 3. Just needs the netaddr package:
pip3 install netaddr
Pretty basic, good enough for CTF or lab use. If you want to change the number of concurrent tasks, just mod line 43 and change the value of max_workers to whatever you desire:
with ThreadPoolExecutor(max_workers=50) as executor: