Which ping implementation is Cygwin using?
It's Windows ping. Just run:
which ping
You'll get:
/cygdrive/c/WINDOWS/system32/ping
Cygwin ping is available on ping package from inetutils source
$ which ping
/usr/bin/ping
$ cygcheck -f `which ping`
ping-1.9.4-1
x86_64 $ ping --help
Usage: ping [OPTION...] HOST ...
Send ICMP ECHO_REQUEST packets to network hosts.
Options controlling ICMP request types:
--address send ICMP_ADDRESS packets (root only)
--echo send ICMP_ECHO packets (default)
--mask same as --address
--timestamp send ICMP_TIMESTAMP packets
-t, --type=TYPE send TYPE packets
Options valid for all request types:
-c, --count=NUMBER stop after sending NUMBER packets
....