Q When surfing the Internet, I frequently see the “Can’t find the server” screen in my browser. This appears unpredictable, but Network Diagnostics often claims that I am connected, or sets the Internet and Server lights to red. How can I investigate this?
A Disconnections are not uncommon, particularly if your modem-router is old, or you have been ‘upgraded’ to variable speed ADSL2+.
If it is the ADSL line that is going down, this should be reflected in the status lights on your modem-router, and in its logs. It is important to view those logs, which you can normally examine by pointing your browser at the modem-router’s LAN IP address, such as 192.168.1.1, and entering the user name and password, by default something like ‘admin’ and ‘password’.
If the drops are actually failing name server lookup, then check your network settings, in the Advanced mode, under DNS. List the modem-router’s IP address first, then your ISP’s name servers, or OpenDNS (126.96.36.199 and .220.220) if you prefer. Also check that your Ethernet cable is securely connected, and try a spare if you can.
More advanced techniques might start with using Network Utility to ‘ping’ the remote site’s IP address. If that works with a low latency, when it confirms that routing to that site should be possible, and suggests that either DNS or you browser could be at fault. However, to go any deeper would probably involve inspecting network packets, which gets technical and tedious.
If the problem persists and none of the above seems to apply, it is always work calling your ISP’s helpdesk. Although the wait might be long, they can sometimes fix stubborn line problems.
Updated from the original, which was first published in MacUser volume 28 issue 13, 2012.