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Table Of Contents  CertiGuide to A+ (A+ 4 Real)
 9  Chapter 14: Networks
      9  What is a Network?
           9  Network Utilities

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TraceRoute (TraceRt)
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PING

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.

The example in Figure 439 shows this request timing out, meaning the destination is unreachable, and Figure 440 illustrates a request that is invalid due to an invalid IP address.


Figure 439: Ping Command - Unreachable Destination

 



Figure 440: Ping Command - Invalid IP Address

 


Figure 441 shows a successful ping, indicating the device is available and responsive.


Figure 441: Successful Ping Command Output

 


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.


Figure 442: Ping Command - Long Response Time

 


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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