No reply for ping command. What does this mean?

I am testing the availability of nodes in a netwok. For that I use ping command and see whether that machine responds back.

However, if a machine is not reachable ping should show me that that "Destination host not reachable". But if it can, it should return back with the response message. But there is no message which is being received!

What does this imply? - That ping is not enabled on that particular machine but reachable on the network ?

4 Answers

Ping is not the best tool to be used to test the availability of a remote network. Although ping can tell you that a network is reachable and send you response times, the lack of that information does not imply that the network is down. As the saying goes, absence of evidence is not evidence of absence.

Open your browser and go to yahoo.com and intel.com. Both come up right? Try pinging Yahoo ping yahoo.com then try pinging Intel ping intel.com Intel doesnt return any ping results. Intel probably disabled ping response for security reasons, like denying ping flooding.

Another issue with ping is that people often misinterpret the results. If you are getting a long response time, people often blame the endpoint. If you are in Windows, type pathping yahoo.com and you will see a combination of traceroute and ping, which gives much better information.

if your on a linux machine, you could use nmap instead

nmap -sP 192.168.x.0/24 

For windows, netscanner.exe is an excellent tool (with a "live display" functionality that shows you host come and go in real time)

-- EDIT --

Since netscanner is not freeware anymore, but trialware (only the first 10 results will be shown), I went looking for alternatives and I came across this free product:

This website hosts many other useful related network tools

It means that your ICMP packet (ping) was silently discarded with no response sent. That might happen for several reasons:

• Ping is disabled on router or (more likely) end point.
• Network is congested or misconfigured

Do not forget that ping is a connection like any other. It must be enabled in the firewall to be accepted and there must be service that listens and sends reply.
In most cases, ping does not work because of firewall settings.
Also do not forget that normally ping returns Connection timeout.. Destination host not reachable. is returned when the IP is not within the network.