An IP number, FQDN or, in the case of a Windows machine, a NetBIOS name can be tested by invoking the Ping (Packet Internet Groper) command from a command prompt.
Figure 441 shows a successful ping, indicating the device is available and responsive.
The middle of Figure 441 shows a line beginning Reply from repeated 4 times, once for each packet the ping command sent. Towards the end of each line is the string time<10ms. This tells us the length of time our packet took to get to the target IP address, and return to us. If you are experiencing slow network access running a ping command may show the response time to be very high. A response under 200ms is perfectly acceptable for normal operations, but responses of 500ms or greater may indicate a network connectivity issue.
In the case of Figure 442, we are pinging a website in Australia so a high response time is understandable.
It should be noted that in some circumstances allowing devices on a network to respond to a ping could be considered a security risk. This is especially true with devices connected directly to the Internet, as responding to a ping is much the same as an escaping prisoner being caught in the prison spotlight you stand out clearly! Some system administrators deliberately prevent their devices from responding to pings, so do not be surprised if a ping, request returns request timed out even though you know there is a working device at the other end. For a practical example, try pinging Microsoft.com.
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