How to Flush your client-side Domain Name System (DNS) cache in Microsoft Windows
In Microsoft Windows start the command window [In XP: Run-> cmd. In Vista and Windows 7: Accessories-> RIGHT-click on Command Prompt->Select "Run As Administrator"] and enter "ipconfig /flushdns" without quotes to flush your local DNS cache.
ipconfig /flushdns
You can also use the command "ipconfig /displaydns" to view your local DNS cache.
How to flush the DNS cache in Mac OS X 10.5 Leopard
Command lookupd no longer exists in Mac OSX Leopard and has been replaced with dscacheutil. The command to flush your local DNS cache in Leopard is:
dscacheutil -flushcache
How to Flush the DNS cache in Mac OS X prior to Leopard
The command to flush your local DNS cache prior to Leopard is:
lookupd –flushcache
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Most DNS clients save or cache the results of name resolution requests; that is the "hostname" to "IP address" conversion results. This speeds up repeat name resolution requests that are common when browsing the web.
Sometimes an incorrect DNS (name resolution) entry, will be cached on your computer. You will need to either flush your local DNS cache or re-boot to get rid of it quickly, or wait up to 24 hours for it to be dropped from your local cache automatically.
Errors in DNS entries on your ISP's DNS Name Servers that are propagated to your local DNS cache are not resolved by flushing your local cache because the defective DNS entry from your ISP's DNS Name Servers will be retrieved and cached again. In this case you must first "use" different DNS name Servers and then flush you local cache.
Updates based on Joel's information about Leopard, EarlyOut's DNS Name server advice about OpenDNS, Me's information about Vista, and edits for clarity.
1. Click the Microsoft Vista Start logo in the bottom left corner of the screen 2. Click All Programs 3. Click Accessories 4. RIGHT-click on Command Prompt 5. Select Run As Administrator 6. In the command window type the following and then hit enter: ipconfig /flushdns
Don't forget (at least, as far as Windows is concerned), after flushing the DNS cache, you want to enter ipconfig /registerdns, release and renew the ip, or, just reboot the machine.
mw-tech wrote: Don't forget (at least, as far as Windows is concerned), after flushing the DNS cache, you want to enter ipconfig /registerdns, release and renew the ip, or, just reboot the machine.
I've never found that to be necessary. It just takes a little longer, at first, to connect to familiar websites because the machine no longer has the addresses cached, and needs to look them up again. There's no need to renew the IP lease, and certainly no need to reboot.
I may have missed it somewhere, but what does the flush accomplish? If I do a flush and that wasn't what is causing my system to run very slow (an average of 6000 kb/s), will it harm annything?
Ciao Ciao asked "What does the [DNS] flush accomplish?"
Most DNS clients save or cache the results of name resolution requests; that is the "hostname" to "IP address" conversion results. This speeds up repeat name resolution requests that are common when browsing the web.
Sometimes an incorrect DNS (name resolution) entry, will be cached on your computer. You will need to either flush your local DNS cache or re-boot to get rid of it quickly, or wait up to 24 hours for it to be dropped from your local cache automatically.
Errors in DNS entries on your ISP's DNS Name Servers that are propagated to your local DNS cache are not resolved by flushing your local cache because the defective DNS entry from your ISP's DNS Name Servers will be retrieved and cached again. In this case you must first "use" different DNS name Servers and then flush you local cache.
And went on to ask "If I do a flush and that wasn't what is causing my system to run very slow (an average of 6000 kb/s), will it harm anything?"
At least for me..
