May 28

Got Stale Cache?

Just like DNS servers, clients cache results. This way, once an entry is looked up, further requests don’t need to take up resources on the server. However, if the DNS is updated after a client caches the result, the two will be out of sync. Typically this doesn’t cause a problem, but sometimes it does. A client can flush its local cache by restarting¬†mDNSResponder as follows:

# sudo killall -HUP mDNSResponder