You're zooming down the information superhighway getting things done when your usually-trusty browser throws up the dreaded "Server not found" message. Argh! Now what?
Roll up your sleeves and get troubleshooting, that's what. When your internet connection goes down or starts acting up, here's what to do.
(First: save this article to your computer's hard drive. It will do you no good out on the internet when you can't get online.)
The best way to resolve ANY computer problem is to use the process of elimination. Narrow down a wide field of possible problems to come up with the right solution. There are two types of connectivity downage: when you can't get to ANY web site or online service at all, and when you can't get to a single specific site or family of sites.
To determine which situation you're in, try getting a response from a few different web sites, including one that most likely is not down, like Google.com, Yahoo.com, or Microsoft.com. At this point command line lovers skip the browser and go straight to ping, a simple tool that sends data packets to a server and receives a response back. Ping a server by typing ping google.com in your Windows command line, Mac's Terminal or shell. You'll see immediately whether or not you're getting a response. In the screenshot here, Google is responding within 106 milliseconds or so.
(Hit Ctrl+C to stop; otherwise ping keeps pinging.) Try to ping google.com or yahoo.com, as well as a few smaller sites like Lifehacker and whatever site you were trying to reach when things went down. If you can't reach Google, Yahoo, Lifehacker or any other site, your whole connection is borked.
If ping ain't your cup of tea, you can also use a web browser to reach a few different sites. Just make sure you try more than one browser when you do, just in case a specific browser's settings or add-ons are actually the problem. Ping is the best way to see if you can reach a given server, not your browser.
Now you know whether your connection is totally down, or if it's just one or a few specific web sites. If you've got more than one computer or device on your network, try the same process on each one to make sure the problem isn't specific to a single computer. You can even grab your Wi-Fi-enabled smartphone, hop on your network, and check to make sure that the same sites or the whole internet are unavailable as well. Is it the same type of downage on all devices and computers? Ok, let's go from there. (If the problem is specific to one computer, skip to Scenario 3.)
Scenario 1: You can't get online at all from any device or computer
In a typical home wireless network, there are three main components: the computer(s) and other devices, your wireless router, and your DSL or cable modem. Of course, many more devices are involved in any network connection from your computer to a web site on the internet, but these are the ones you have control over. If you've been surfing away happily on your computer on your home network and then for no apparent reason you stop being able to go down, the first places to check are your modem and router (which might be the same device).
Twitter user Jesse Glacken put it well (and geekily) when he described what he does to fix a broken connection.
In non-programmer style English: If your modem's lights are out, reboot it. If your router's lights are out, reboot it.
In short, rebooting the modem and the router will solve 90% of your home internet connectivity problems. Generally I unplug the router first, then unplug the modem. (Many don't have power buttons, so it's often a matter of pulling the power cord out of the box.) Count down to 10, then plug the modem back in and then the router. Give them both time to boot up and connect by watching the activity lights. Then try connecting to the internet again on your computer.
At this point, if all the lights are on but you still aren't getting ping responses or are able to load web pages, it's time to continue down the elimination road. Grab the cable that your ISP gave you and connect your computer directly to the modem to eliminate the router. Reboot the modem again. Try pinging or getting online. No dice? It's time to call your ISP.
If you can get online while you're connected directly to your modem, but not when you're connected to your router, the problem is somewhere on your router. Unless they've installed the router for you, most ISP's won't offer tech support for your router. Troubleshoot it by visiting its administrative page and checking whether or not it's getting a connection from your provider. This is the time you want to have your router's user guide handy. Skip down to Scenario 4 for more on the care and feeding of a troubled router.
Scenario 2: You can't get to a specific web site or set of web sites from any computer or device
If it's just one web site that you can't reach, the problem most likely isn't you; it's that web site's server.
My favourite tool for checking a web site is the super-useful Down For Everyone Or Just Me tool, which tells you if the whole world can't reach that web site as well. If it's not just you, and that web site is indeed unavailable to anyone, use Notify Mee to get an email alert when that web site is back up. (Thanks, warplayer!)
If it turns out it is just you, you're in an interesting pickle. You can reach DownForEveryoneOrJustMe.com and Google.com, but not this particular web site—but the rest of the world can. At this point, it's time to start thinking about DNS servers. Your ISP's DNS servers are the ones which figure out what internet domain names (like lifehacker.com) map to what IP addresses. If your ISP's DNS server doesn't have the correct address for a web site name, you're not going to the right server. To see if the problem is DNS, try switching to the free OpenDNS service.
To get more exact information about the source of the problem, skip down to the section on using traceroute.
Scenario 3: One computer can't get to certain web sites, but other computers on the same network can
If you're here reading Lifehacker, chances are your computer is free and clear of viruses and other malware. If you're visiting Aunt Mitzy and Uncle Ralph, however, that might not be the case. If a specific computer can't get online but other devices can, the problem is local to that machine.
First, make sure the problem isn't browser-specific. Install Firefox and check to see if you can get online with it. Try Chrome as well. (If the computer can't get online at all, use one that can to download the browser installation files, or bring along a portable version on a thumb drive.)
If all the browsers on the system can't get online, disable the anti-virus software and check the firewall. Sometimes corrupt AV software that's not entirely turned off or uninstalled can mess with the network connection. Try creating a whole new user on the system and logging in as that new user to make sure no process is running in the background that's getting in the way. If you suspect malware IS at work, scrub down the machine. In the worst case scenario of a totally crap-laden system, wipe the hard drive clean and install Windows from scratch.
Scenario 4: Your router requires constant resets or slows down connections
If your wireless router seems to slow down your connection or goes on vacation often and without warning, there are a few things you can do.
For routers that become unreachable or lose connectivity often, try updating the firmware to the latest version. Search the router's manufacturer's web site for the latest and greatest and install it using your router's administrative interface. If you're feeling very adventurous and have compatible hardware, try third-party firmware like DD-WRT or Tomato.
For router slowdowns, try reducing interference or changing the wireless channel. The New York Times advises:
The base station may be getting interference from a new nearby device that was recently installed and is using the same radio frequency. This can include cordless phones, microwave ovens, baby monitors, wireless speakers, mice or keyboards. See whether the network speed improves when these devices are moved or turned off. Moving the base station itself may also help.
For apartment dwellers, having neighbours with their own wireless networks crowding the airwaves may also impair performance, especially if everyone's network is set to use the same default channel. To change the router's channel, you need to go into its configuration file (you usually need the base station's password to gain access to these settings). The steps for changing the channel will vary based on the manufacturer, but Linksys has its instructions at snipurl.com/3iibn. Apple's AirPort and AirPort Express base stations can be adjusted by using the AirPort Utility software. Experiment with Channels 1, 6 or 11, as they are far enough apart not to overlap with other channels and may provide a better network signal.
The Command Line Tool of Network Ninjas: traceroute
Every good network administrator reaches for the age-old command line tool traceroute to troubleshoot broken network connections. Traceroute maps the path data packets take from your computer to a web site, and includes every single stop along the way and how long it took to get there. For broken connections, traceroute reveals at what exact point the broken connection is failing, and gives someone with a little knowledge of ping and IP addresses more information about how to resolve the problem.
To give traceroute a spin and see what its output looks like, try this online version (which obviously doesn't help if you can't get online at all).
To run it from your computer, on Windows from the command line type tracert google.com (notice the missing o, u, and e). In a Mac Terminal window, type traceroute google.com. Check out this awesome traceroute tutorial or this traceroute primer to learn more on interpreting traceroute output, which will look something like this on a broken connection where the connection fails on hop 4:
What are your most common internet connection maladies? How do you resolve them? Drop your network troubleshooting knowledge in the comments.
Gina Trapani, Lifehacker's founding editor, never wants to see a "Server not found" message again. Her feature Smarterware appears every week on Lifehacker.