ipconfig /flushdns ipconfig /displaydns [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters] petri.co.il reports the following value works on all: 2000/XP/2003 http://www.petri.co.il/preventing_caching_of_failed_dns_lookups.htm NegativeCacheTime=0 MaxNegativeCacheTtl=0 (DWORD, default value: 0x12C (300 seconds), range: 0x0–0xFFFFFFFF seconds) Description: Determines how long an entry recording a negative answer to a query remains in the DNS cache. When the time specified in the value of this entry expires, the DNS client deletes the answer record from cache. This is a Windows XP and 2003 Server setting only, the Windows 2000 equivalent is NegativeCacheTime. NegativeCacheTime=0 (DWORD, default value: 0x12C (300 seconds), range: 0x0–0xFFFFFFFF seconds) Description: Determines how long an entry recording a negative answer to a query remains in the DNS cache. When the time specified in the value of this entry expires, the DNS client deletes the answer record from cache. This is a Windows 2000 only setting, please use the MaxNegativeCacheTtl for Windows XP and 2003 Server instead. NetFailureCacheTime=0 (DWORD, default value: 0x1E (30 seconds), range: 0x0–0xFFFFFFFF seconds) Description: Determines for how long the DNS client stops sending queries when it suspects that the network is down. When the DNS client does not receive responses to repeated queries sent to any network adapter, the DNS client stops sending queries for the time specified in the value of this entry. During that time, the DNS client returns a timeout response to all queries. If the value of this entry is 0x0, this optimizing feature is disabled. DNS continues to send queries to an unresponsive network. NegativeSOACacheTime=0 (DWORD. default value: 0x78 (120 secnds), range: 0x0–0xFFFFFFFF seconds) Description: Determines how long an entry recording a negative answer to a query for an SOA (Start of Authority) record remains in the Domain Name System (DNS) cache. When the time specified in the value expires, the DNS client deletes the answer record from the cache. Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters] "NegativeCacheTime"=dword:00000000 NegativeCacheTime 0