Tools Overview
Your first lines of defense in network troubleshooting are common applications, the Mac operating system, and bundled utilities. Applications are the easiest methods of testing a connection, while using the utilities/diagnostics are more important in advanced troubleshooting of unresolved issues. Remember, one of the first things you must determine is whether your issue involves a single computer, multiple computers on your local network (your LAN), your ISP's equipment (WAN), or the Internet site you are trying to access. Since the Internet as a whole does not fail entirely, even large Internet-related problems are usually isolated to a single ISP, a small part of the overall Internet, or just a single website or server.
Applications
Use the following applications to help you verify network problems and narrow your focus.
Safari
You can use a browser, such as Safari, to determine if an Internet problem is isolated to a specific site or to your connection through the Internet to that site. If the browser displays an error when accessing one site but not another, the problem is likely with just that site. Using an alternative browser, such as Internet Explorer or Firefox, may reveal whether the problem is related to a specific browser's interaction with the site.
Attempting to send and receive email from a mail client, such as Mail, can help you determine if you have a functioning SMTP connection. If you can't get mail but can surf webpages, you have a POP, IMAP, or SMTP issue. Conversely, if you can get mail but can't surf webpages, you have an HTTP-related issue.
If you use Mac OS X 10.4 Mail, an additional tool is available to you. It's called the Mail Connection Doctor, and it checks all relevant functions of your incoming and outgoing mail servers for connectivity and validity, alerts you to any problems, and suggests troubleshooting techniques.
iChat
iChat instant messages can be transmitted over the Internet (WAN) via its connection with the AOL Instant Messaging (AIM) protocol and service, or locally over a wired or wireless LAN via the Bonjour protocol. If you can send instant messages locally via Bonjour to another iChat client on your LAN, but not to anyone else over the Internet via AIM, then you might have a WAN issue that could be preventing this communication.
There also is a Connection Doctor in iChat, which displays the audio and video stream throughput for both the local and remote sides of the chat. You can use this tool to help determine if there are any network bottlenecks that may be preventing you from communicating via iChat.
Operating System
Use the following operating system functions to help you verify network problems and narrow your focus.
Connect to Server
Choosing Connect to Server (Command-K) from the Go menu in the Finder may help you determine where a connection failure is occurring. Can you see any other servers or shared Macintosh or Windows computers on your local network (LAN) when you attempt to connect or browse using the Connect to Server command? Can you connect to a specific server that you're sure you should have access to? Can you connect to other computers using AppleTalk? Answering questions such as these can help you isolate the issue before reaching for one of the utilities discussed in the next section.
Network Preferences
Of course, the obvious place to check when experiencing connectivity issues is Network preferences. Are the status indicators green, indicating a functioning Internet connection? Or are they yellow or red, indicating a more basic problem, such as a self-assigned IP address? Check the TCP/IP settings, server addresses, and so on. When in doubt, use the Network Assistant in Network preferences to create a new network location configuration. This will verify that all Network preference settings are correct, while leaving the existing settings unchanged.
Utilities
Use the following utilities to help during the diagnostics, research, and repair steps of the troubleshooting flowchart.
System Profiler
System Profiler is a Mac OS X utility that gathers and displays information about your computer. It can show you what internal components the operating system installed and recognizes, what external peripheral devices are connected, what software is installed, what version and build of Mac OS X you are using, the serial number, and much more. Although System Profiler is not a diagnostic utility, you can use it during troubleshooting to verify whether the operating system can recognize installed internal hardware components (such as RAM or an AirPort Extreme Card) and external connections (such as network connections).
Network Diagnostics
Network Diagnostics is a new, powerful troubleshooting utility in Mac OS X 10.4 Tiger. It automates many of the troubleshooting steps outlined later in this lesson, and provides context-sensitive step-by-step instructions that can assist a user in isolating a specific networking issue. It works with built-in Ethernet, internal modem, or AirPort connections, and several Mac OS X 10.4 applications such as Finder, iChat, Mail, and Safari have been updated to take advantage of Network Diagnostics when a network connectivity issue arises. For more information, search Mac Help for “network diagnostics.”
Network Utility
Network Utility is a very powerful tool for gathering information and troubleshooting network connection issues in Mac OS X. Network Utility combines several network troubleshooting tools into a single application. Many of these tools are available in the Terminal (via the command line); Network Utility provides a simple GUI for these tools. For example, one function of the Network Utility enables you to perform a simple network test, known as a ping, to verify network connectivity to a designated URL or IP address.
Apple Hardware Test
Apple Hardware Test (AHT) detects problems with the computer's internal hardware components such as the logic board, memory, modem, video RAM (VRAM), and AirPort Card. It does not check externally connected hardware components such as USB or FireWire devices, nor does it check non-Apple devices such as PCI cards from other vendors. AHT does not test networks, but because it can verify proper computer functionality, it can help eliminate your computer as a suspect during your network troubleshooting.
AirPort Management Utility
Found on the software CD included with the AirPort Extreme Base Station, AirPort Management Utility (AMU) enables you to view base station logs and visually compare configuration settings for multiple base stations.
Console
Console is a Mac OS X utility that displays log files. A log file is a text file that contains messages from applications and various parts of Mac OS X. The main benefit of reading log files is that they can give you more information about an issue than an error message in a dialog. Since each entry in each log file is time and date stamped, you can use Console to research past events or to help troubleshoot an issue that you can readily reproduce (like failing to connect to the Internet, for example).
Terminal
UNIX is the foundation of Mac OS X. Terminal provides a method of accessing the UNIX command line. Most customers will not be comfortable using UNIX commands directly and typically will never need to use Terminal. However, some service and support technicians may prefer to use Terminal when troubleshooting various problems, such as network issues. The troubleshooting recommendations and steps in this book will not focus on UNIX Terminal commands, and instead will use GUI utilities wherever possible.