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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP Administration and Troubleshooting Utilities and Protocols

Previous Topic/Section
TCP/IP Host Name Utility (hostname)
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4
5
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TCP/IP Route Tracing Utility (traceroute/tracert/traceroute6)
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TCP/IP Communication Verification Utility (ping/ping6)
(Page 4 of 5)

Methods of Diagnosing Connectivity Problems Using ping

Most people find that using ping with default settings is enough for their needs. In fact, the utility can be used in this simplest form to perform a surprising number of diagnostic checks. In many cases, the ping command can be used to diagnose connectivity problems by using it multiple times in sequence, often starting with checks at or close to the transmitting device and then proceeding outwards towards the other device with which the communication problem has been observed. Some examples of how ping can be used in this way:

  • Internal Device TCP/IP Stack Operation: By performing a ping on the device’s own address, you can verify that its internal TCP/IP stack is working. This can also be done using the standard IP loopback address, 127.0.0.1.

  • Local Network Connectivity: If the internal test succeeds, it’s a good idea to do a ping on another device on the local network, to verify that local communication is possible.

  • Local Router Operation: If there is no problem on the local network, it makes sense to ping whatever local router the device is using to make sure it is operating and reachable.

  • Domain Name Resolution Functionality: If a ping performed on a DNS domain name fails, you should try it with the device’s IP address instead. If that works, this implies either a problem with domain name configuration or resolution.

  • Remote Host Operation: If all the preceding checks succeed, you can try pinging a remote host to see if it responds. If it does not, you can try a different remote host; if that one works, it is possible that the problem is actually with the first remote device itself and not with your local device.

Note: While the inability to get a response from a device to a ping has traditionally been interpreted as a problem in communication, this is not always necessarily the case. In the current era of increased security consciousness, some networks are set up to not respond to Echo messages, to protect against attacks that use floods of such messages. In this case a ping will fail, even though the host may be quite reachable.


Key Concept: The TCP/IP ping utility is used to verify the ability of two devices on a TCP/IP internetwork to communicate. It operates by having one device send ICMP Echo (Request) messages to another, which responds with Echo Reply messages. The program can be helpful in diagnosing a number of connectivity issues, especially if it is used to test the ability to communicate with other devices in different locations. It also allows the average round-trip delay to exchange messages with another device to be estimated.



Previous Topic/Section
TCP/IP Host Name Utility (hostname)
Previous Page
Pages in Current Topic/Section
123
4
5
Next Page
TCP/IP Route Tracing Utility (traceroute/tracert/traceroute6)
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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