Posted by (author unknown) at MacOSXHints.com
I came across this Apple technical note this morning, which describes how to flush the DNS cache on your Mac. We have a hint for 10.5, which is also valid for 10.6, but we’re not up to date.
So, as a reminder, to flush the DNS cache in Mac OS X 10.5 and 10.6, run this command in Terminal:
sudo dscacheutil -flushcache
To do the same in 10.7 and 10.8, run this command:
sudo killall -HUP mDNSResponder
As Apple points out, you might need to do this in the following situation:
“OS X keeps a local cache of resolved DNS queries for a time defined by the DNS server, but sometimes it may be necessary to reset the cache immediately and re-query a DNS server. For example, you might do this after an entry on the server is changed or a new entry is added.”







