NEC UNIVERGE SV9100 Manual page 29

Unsuccessfull PING
If you are unable to ping a device it may mean that either the source or destination device:
is not configured correctly
is not connected to the LAN (e.g. cable disconnected)
has a developed a fault
or any device in between the source or destination may be faulty (e.g. routers)
Pinging from a PC
The command syntax for ping is: ping [-t] [-n count] [-l size] target
-t (optional) continually sends PING requests until Ctrl-C is pressed to cancel
-n (optional) sends a specified number of PING requests
-l (optional) sends packets of a specified size (bytes)
target the destination IP address or host name
Part 1: VoIP Reference Manual 29