Once you go to a Web site, or do any DNS lookup, the IP gets cached for quite a while. This becomes a royal pain if you’re a systems administrator who is in the middle of migrating domains from one server to another. Executing
clears the cache, restarts the caching daemon, and fetches fresh DNS records. And there was much rejoicing…
sudo killall lookupd lookupd -flushcache
Updated November 26, 2007: Thanks to Syd, the Leopard (Mac OS X 10.5) command has changed to
dscacheutil -flushcache and
lookupd has been deprecated.