Networks are a fickle thing. Every so often your network, which ever method you are using, will just suddenly stop. This can be a right pain and usually happens right before you have to buy something off ebay, at that crucial time. This guide will hopefully enable new users (as well as those pro’s) to troubleshoot your own network before you have to phone a techie friend or a company. This guide is designed to be followed one after another, although you can skip to any point. I recommend you read the Anatomy Of Network Preferences, before you begin.
Switch It Off And On Again
If you have ever watched or heard of The It Crowd, one of the main jokes in the show is it switch there computers on and off again. This usually works for network problems. For instance it can usually be a good idea to unplug your network cable, leave it a minute or two and then plug it back in again. This gives any network components chance to re-register your Mac into the system. Can usually solve most DHCP errors. This tip can also extend to switching off and on, routers switches or even your computer. This problem may be hardware side, if it happens persistently it might be a good idea to buy new hardware. Usually start with cables and move up to switches, routers and maybe even your Mac’s LAN card.
Use Network Diagnostics
One tool that may be useful to analyse network problems is to use Network Diagnostics. This can be found in /System/Library/CoreService or from any 404 page in Safari. This tool can be used to see where you have problems along the network path and can be used to find problems.
Disable Network Interfaces
It can be hard to juggle more than one conversation at a time. Now imagine you have to do this a thousand times faster. This is the type of thing you Mac has to handle. If you have multiple interfaces connected to a network. Whether it be LAN, Wi-Fi or Firewire, all these connected to the same, or different points, can cause errors as you Mac send information to the wrong sources. The best way to handle problems is to delete the interfaces. Do this by selecting the interface in System Preferences, and pressing the minus button at the bottom of the sidebar.
Check Your Settings
If something has gone wrong on your Mac, usually the problem is down to your settings have been changed. Go through and check them all. If an IP address has been set back to default this can cause a whole load of errors. Go through the Network Settings of the interface you are using and check every setting to make sure it is correct. Change any settings as needs be. Also check settings on routers and other network hardware, settings could have been changed there.
Refresh The DNS
All computers use DNS servers to ask for webpages to IP addresses. This DNS uses a cache to save having to run hundreds of commands every time your surf the web. To refresh your DNS, read this article I published a while ago. If you still have trouble accessing web pages I recommend you change, or add, the OpenDNS servers to your list. More information on how to do this can be found here.
Hopefully this little guide is useful to yourself. Its not a full manual to help you diagnose every problem, but it will solve 99% of the problems. If you do have major network problems it might be a good idea to get some help.