This article is an introduction to basic network troubleshooting concepts.
Imagine you try to view a web site, and the pages load slowly or not at all. When this happens, it is useful (though sometimes a bit tricky) to determine where the problem is occurring. For example, is the web server experiencing issues? Or the network connection between your computer and the server? Or maybe even your computer itself?
To help answer these questions, you can use various tools to do some basic network troubleshooting. Some of these tools are run from the command line. Alternatively, many web sites provide online versions of these tools that you can use in your web browser.
Sometimes you just want to know if your computer can reach a remote host. To test basic network connectivity, you can use the ping tool. Ping enables you to quickly determine if a remote host is available. For this reason, it is often the first thing administrators do when troubleshooting network issues. The ping program works by sending a special type of packet to the host and then waiting for a response back. If a response is received, then basic network connectivity exists between the remote host and the local computer.
The traceroute (or tracert on Microsoft Windows) tool enables you to view the complete route network packets take from your computer to a remote host. Whereas ping simply tells you if a remote host is active and responding to ping requests, traceroute provides much more detail about the actual route packets follow from one host to another. For example, traceroute can help you determine if (and where) there is a bottleneck in the network connection between your computer and a remote host.
For more information about how to troubleshoot network connectivity issues and how to use these tools, please see this article.
For troubleshooting DNS (domain name server) issues, you can use tools like dig and nslookup, which enable you to do detailed DNS lookups for a given host. For example, you can quickly determine the IP address associated with a given domain name, or confirm a domain's mail server settings.
For more information about how to troubleshoot DNS issues, please see this article.