How to Verify Your Snow Leopard’s Network Connectivity - dummies

How to Verify Your Snow Leopard’s Network Connectivity

By Mark L. Chambers

After you have your Macs connected and your TCP/IP configuration is done, check to make sure that everything is working. After you have at least two computers on your network, each with a TCP/IP address, you can use a simple little utility called ping to test the connection.

ping is a very simple, yet extremely helpful, utility that’s the first connectivity-testing tool out of the box, even for network professionals. When you use the ping utility — referred to as pinging something — the application sends out a small packet of data to whatever destination you’re trying to reach. When the receiving computer hears the ping, it answers with a ping reply. If the original computer receives the ping reply, you know that the connection between the computers is good.

To ping a computer, you use a little application built in to Mac OS X called Network Utility, which allows you to work various network wonders (including checking connectivity, watching the route that your computer takes to get to another computer, and looking up information about Internet domain names). To use Network Utility to check network connectivity, follow these steps:

  1. Open a Finder window, click Applications, and click Utilities.

  2. Double-click the Network Utility icon to launch the application.

  3. Click the Ping tab.

    Ping to test network connectivity.
    Ping to test network connectivity.
  4. In the Enter the Network Address to Ping text field, enter the IP address of the computer that you want to ping.

  5. To simply verify connectivity, select the Send Only x Pings radio button and enter a low number, such as 5, in the text field.

    Five or ten pings are plenty to see whether the connection is good.

  6. Click the Ping button.

    Your Mac sends ping packets to the IP address that you entered.

If the pings are successful, text appears in the text box at the bottom of the Ping tab: one line for each ping reply received from the other computer. The end of each line reads time= with a number at the end. That number is the amount of time, in 1/1000 of a second (milliseconds), that it took for the ping packet to go from your computer to the other computer and back.

If your ping is unsuccessful, you see nothing, at least for a little bit. Each ping that you send takes two seconds before it’s considered missing in action. So, if you choose five pings, wait ten seconds before you see the results. After all the pings time out — a ping times out when it doesn’t get returned in the proper amount of time — you see a line of text appear that reads ping: sendto: No route to host or 100% packet loss. Both error messages mean the same thing: All the ping packets that you sent out are now in the packet graveyard, never to be seen again. As you’ve likely guessed already, this is not a good sign for your network connectivity.

If you can ping all the other computers on your network from one of the computers, you don’t need to go to each computer and ping all the others. You can logically assume that all the computers can communicate. For instance, if you can ping computers B, C, and D from computer A, you don’t need to bother with ping tests from computer B, C, or D.

After you have your computers configured and you’ve verified connectivity among them, start doing the fun stuff that a network allows you to do, such as sharing data, printing, and (most important) playing games with users on other computers.