Ping is used to troubleshoot connectivity. You might use ping to test a network printer or copier connection to determine whether a device is offline or to verify you can connect to a router. If a ping comes back with fast response times, your connection is good so the problem likely lies with the server or application.
Almost any network-connected device will respond to a ping which makes it incredibly valuable to check networking connections. Ping can be used to test routers or servers for throughput and speed. You can also ping across a range of addresses to find each attached device in a particular range. You can test computer names and addresses of computers. A ping command can be run manually or automated as a scheduled task for monitor network reliability.
If the ping command does not get a response from the host, you will see either nothing returned or get a timeout notification. Since it's sending 4 requests, you'll likely see four time out notices. The Ping command allows you to add modifiers or parameters also called switches to customize the command for troubleshooting. Here is a list of the commands and the proper syntax in which to use them for Windows, although you will find slight variations for Unix.
The order in which you use these switches is important. Every second of the day there are untold millions of pings flashing back and forth between computers on the Internet like a continuous shower of electronic neural sparks. The following subsections provide information on how Ping was invented, how Ping works, how to use Ping, Ping web sites, and info on the original Unix Ping version.
However, the modern Internet Ping command refers to a program was written by Mike Muuss in December, , which has since become one of the most versatile and widely used diagnostic tools on the Internet. Muuss named his program after the sonar sounds used for echo-location by submarines and bats; just like in old movies about submarines, sonar probes do sound something like a metallic "ping".
The IP address Therefore, a ping to that address will always ping yourself and the delay should be very short. This provides the most basic test of your local communications. You can use the Ping command to perform several useful Internet network diagnostic tests, such as the following:.
Access : You can use Ping to see if you can reach another computer. If you cannot ping a site at all, but you can ping other sites, then it is a pretty good sign that your Internet network is working and that site is down. On the other hand, if you cannot ping any site, then likely your entire network connection is down due to a bad connection. For example, a web site hosted on your neighbor's computer next door with a different Internet service provider might go through more routers and be farther away in network distance than a site on the other side of the ocean with a direct connection to the Internet backbone.
If a site seems slow, you can compare ping distances to other Internet sites to determine whether it is the site, the network, or your system that is slow. You can also compare ping times to get an idea of which sites have the fastest network access and would be most efficient for downloading, chat, and other applications.
If you ping a domain name, it helpfully displays the corresponding IP address in the response. You can run the ping command on a Windows computer by opening a command prompt window and then typing "ping" followed by the domain name or IP address of the computer you wish to ping. Warning: Using the debug ip packet command on a production router can cause high cpu utilization. Since no routing protocols are running on Router1, it does not know where to send its packet and we get an "unroutable" message.
Router1 is correctly sending its packets to Router2, but Router2 doesn't know how to access address This is slightly better. Router1 is sending packets to Router4, but is not getting any answer from Router4. Router4 receives the ICMP packets, and tries to answer to This is a situation where the interface stops working. In the example below, we try to ping Router4 from Router Since the routing is fine, we will do the troubleshooting step-by-step.
First, let us try to ping Router From the above, we see that the problem lies between Router2 and Router3. One possibility is that the serial interface on Router3 has been shut down:.
In this scenario, we want to allow only telnet traffic to enter Router4 through interface Serial0. Refer to the Use the Debug Command section for using access lists with debug commands. At the end of an access-list command, we always have an implicit "deny all". This means that the ICMP packets that are entering the Serial 0 interface on Router4 are denied, and Router 4 sends an ICMP "administratively prohibited unreachable" message to the source of the original packet as shown in the debug message.
The solution is to add the following line in the access-list command:. In this example, the ping is not working due to "encapsulation failed".
This means that the router knows on which interface it has to send the packet, but does not know how to do it.
See Configuring Address Resolution Methods for a detailed explanation. You can check this mapping using the show arp command:. Return to the "encapsulation failed" problem.
We get a better idea of the problem using this debug command:. Here, the If we do not get an answer, the corresponding address in the show arp output is marked as incomplete:. After a predetermined period, this incomplete entry is purged from the ARP table. As long as the corresponding MAC address is not in the ARP table, the ping fails as a result of "encapsulation failed".
By default, if you do not receive an answer from the remote end within two seconds, the ping fails:. The list above uses a kind of outside-in approach, where you ping the furthest destination first, and then work your way in to the more local devices. Some people like to work inside-out by pinging the loopback address first, then their router or another local device , and then an internet address.
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