One of the more frustrating parts of web development is waiting for DNS propagation - in other words, if you change which server a domain name points to, it takes a while for that information to filter through the interwebs (different Internet Service Providers have their own DNS caches, and it takes a while for them to reset). The result of this is that some people may be seeing the old server while others see the new one. This process can take up to 72 hours. As a developer, there is very little you can do about DNS propagation - it’s out of your hands (although try explaining that to a client….).
Propagation is only one part of the equation, however. Chances are pretty good that, beyond the DNS flushing that needs to happen on the part of your ISP, you also will have an IP cache issue going on with your local machine, at least if you develop on Mac OSX like we do. While you can’t control the length of time it takes your ISP to clear out their cache, you can at the very least make sure that when the propagation happens, you are the first to see it. In Mac OS X, the way you do this is to clear your machine’s IP cache, and clearing your browser cache. This is a pretty simple process, but it involves the big bad Terminal.
- Open the Terminal application
- Enter the following text after yourname$
- OSX 10.5 Leopard and Above, enter:
dscacheutil -flushcache - OSX 10.4 and Below, enter:
lookupd -flushcache
- OSX 10.5 Leopard and Above, enter:
- Hit Return
- Relaunch your web browser, clear your browser cache (if you’re using Firefox, I highly recommend the Cache Status plugin: https://addons.mozilla.org/en-US/firefox/addon/1881)
- Reload the site you are trying to see
If propagation has happened at your ISP level, you should now be able to see the site living on the new server.
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