By Graham K. Rogers

Beware tampering. I fell into one of my own traps this week when a colleague offered me a connection to a new router he had bought on eBay. This worked at the faster 802.11ac networking speeds, like my Airport Express router at home. The internet is no faster, but data transfer between devices is improved: at least in theory.

Along with the new network came the news that the university no longer restricts users to one device: completely impractical these days with the proliferation of mobile connections; and in any case, many these days will have at least two computers: a notebook and an office desktop.

The university still has its proxy setup, like many organisations and I entered the details. Fine: nice speeds. The only problem was when the network was disconnected (out of the office with iPhone, or computer idle), it took almost a minute for the new router to reappear in the list of available devices. Once I knew this was the norm, I could adjust.

At home I used the iPhone and the iPad Pro to connect to the internet and did not use the MacBook Pro at all that evening. The morning ritual is a little different with a look at the news on an iPad first, then email and work on the Mac. This morning, although I had the internet on the iPad, there were no pictures in the email. Then I noticed none appearing in Twitter. Neither of these is particularly unusual; but then I accessed a web page from email and it would not load.

Diagnostics here start with trying Apple's main page. If that doesn't work, there is a problem and I need to dig deeper. I could see that there was some data downloading, so tried FTP and that worked. Suspicions began to fall (not for the first time) on the connection via the university link the day before; but there were still a few other things to try.

The Mac App Store failed to load, as did the iTunes store when I restarted that app. With FTP working, the 80 and 8080 web ports were the problem. I restarted the router, but that made no difference, and the iOS devices were fine anyway. The problem was clearly with the Mac, so I restarted that.

After the restart there was no difference. I used the Option click on the WiFi icon in the menubar to see more information about the connection (all good) and used Wireless Diagnostics which reported the connection was fine. Firewall, OK.

I should have looked earlier of course, but I finally checked System Preferences > Network. The connection was right and it was shown as live; but in Advanced I finally saw that the Proxy settings were active. Slap of forehead. Instead of changing the location, I had used the Home settings and the proxy was now active for home too.

The default is Automatic, but by editing this and adding a new location, different settings can be created depending on which networks are being used. As well as Home I also have Work and an Out & About setting for when I am travelling. I ought to have switched to the Work location before entering the new router details at my office.

I unchecked the Proxy settings for the Home connection and all was well. At the office, I switched to Work settings and the Proxy details already entered worked correctly on any network connection using the university system.

Graham K. Rogers teaches at the Faculty of Engineering, Mahidol University in Thailand. He wrote in the Bangkok Post, Database supplement on IT subjects. For the last seven years of Database he wrote a column on Apple and Macs. He is now continuing that in the Bangkok Post supplement, Life. He can be followed on Twitter (@extensions_th)