You can do a network scan that sends one ping packet per/IP:

fping -a -r 0 -g 172.31.0.0/24

Or 4 ping packets per/IP (the "-r" is for retry):

fping -a -r 3 -g 172.31.0.0/24

You can do an even faster network scan by by adding "-i 1" switch (Requires sudo, waits 1ms between pings):

sudo fping -a -i 1 -r 0 -g 172.31.0.0/24

You can do the same fast scan, but from a host-list like this:

sudo fping -a -i 1 -r 0 < host_list.txt

You can add "-s" to any scan to show cumulative statistics upon exit:

fping -s -a -r 0 -g 172.31.0.0/24

Check the man page for any other options, or leave a comment below and we can try to help: