OS X: How to reset the DNS cache
Learn how to reset (flush) the DNS cache.
OS X Mountain Lion or Lion
Use the following Terminal command to reset the DNS cache:
sudo killall -HUP mDNSResponder
Mac OS X v10.6
Use the following Terminal command to reset the DNS cache:
sudo dscacheutil -flushcache
Additional Information
When you might want to do this
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.