Every now and then I do something really idiotic. I try not to, but perhaps there is a "Conservation of Stupidity" thing at work in the universe which means that every half way clever thing Robert does must be compensated for with an action of outright daftness.
Anyhoo, yesterday I was working on www.wherewouldyouthink.com, a little site for use by anyone thinking about university. It has a bunch of bits and bobs about student life and whatnot. And I was re-hosting it all using glorious Squarespace Version 6. To make this work I had to update the DNS settings for the site. And I remembered that I'd done that for this venerable site only recently, so I might as well copy those settings. So I opened up my doman name hosting folks and made some adjustments. And by mistake I ended up changing the IP address of my two sites to completely the wrong values. This turned out to be a very, very, silly thing to do.
The IP address is like the telephone number of a host on the internet. It is now part of popular culture. There is usually a point in a crime/spy caper where the evil guys have been posting things on the internet and one of the tech guys says "I've got their IP address, let's go..." Cue onscreen map, squeal of rubber as cars hurtle down ramps and gunfight before end credits.
We don't like having to remember phone numbers, so we have an address book in our phones that maps names onto the appropriate digits. This saves us work and it is also useful because when someone gets a new handset you can just update their number and stay in touch.
The internet works in just the same way. Normally we don't bother with 18.104.22.168, instead we put www.robmiles.com into our browser. But something has to do the mapping of names to numbers, and that something is the Domain Name Service, or DNS for short. This is like the address book for the internet. It is very cleverly designed, with a hierarchy of servers giving out addresses for names.
If your computer asks the local network for a host and the network server doesn't know the address of that one it will ask the one above, and so on to the very top of the tree. When a new name is added to the internet it is added to the very top site and eventually the name/address pair percolate down to the all the machines in the tree.
Each server will keep local copies of the address values so that it doesn't have to keep asking the one above it for help. But every now and then it checks to see if the copy it has is up to date. This means that if the address at the top changes it takes a while for this to have an effect.
So when I broke my DNS settings everything kept going for a while. But then my site started to become inaccessible. And in a very strange way. Depending on which network I used, the site would either work or it wouldn't, depending on whether the DNS data was "fresh" or "old".
Of course I figured out what had happened very quickly, and fixed it fast. But it still took the best part of a day for things to settle down and return to normal. Oh well, I'll be a lot more careful in future when I fiddle with those numbers.