If you enter ipconfig /displaydns at a command prompt you’ll see that Windows stores successful and unsuccessful name resolutions in cache. By default, Windows will store this cache for 24 hours. You can adjust this by doing the following:
Open the registry editor and navigate to:
The entry 14400 is in seconds. Enter this as a Decimal Base and NOT Hexadecimal.
Ipconfig /flushdns flushes these entries manually.