Flushing Leopard’s DNS Cache
This post applies to Macintosh OS X version 10.5 and later.
From Apple’s manual page:
dscacheutil does various operations against the Directory Service cache including gathering statistics,
initiating lookups, inspection, cache flush, etc. This tool replaces most of the functionality of the
lookupd tool previously available in the OS.
The following command flush the entire DNS cache:
dscacheutil -flushcache
Mac OS X Manual Page for dnscacheutil