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How to Flush your local DNS cache

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Problem Solver

How to Flush your local DNS cache

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

 

--------------------0---------------

 

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.

 

Domain Name System at Wikipedia.

 

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.

Message Edited by CWH803 on 02-03-2010 09:13 AM
Most Valued Poster

Re: How to Flush your local DNS cache

Important slight difference in Windows Vista...
 
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
Added....
 
Everything you wanted to know about the "Run" command in Vista.... http://www.computerperformance.co.uk/vista/vista_run_command.htm 


Message Edited by Me on 11-30-2007 03:12 PM
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Heroes aren't born...they volunteer...
Problem Solver

Re: How to Flush your local DNS cache

Thanks for that link, ME, it appears to be an easy to read and understand site..  Smiley Wink At least for me..
 
ciao, bj
Bronze Problem Solver

Re: How to Flush your local DNS cache

How to flush DNS in Mac OS X 10.5 Leopard

lookupd no longer exists Mac OSX Leopard, and has been replaced with dscacheutil. Therefore, the command to flush DNS cache in Leopard is:

dscacheutil -flushcache
Tags (2)
Contributor

Re: How to Flush your local DNS cache

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.
Most Valued Poster

Re: How to Flush your local DNS cache



@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.
Frequent Visitor

Re: How to Flush your local DNS cache

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?
Problem Solver

Re: How to Flush your local DNS cache

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?"

No.

Message Edited by CWH803 on 08-31-2009 08:30 AM
Expert

Re: How to Flush your local DNS cache



CWH803 wrote:

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?"

No.


 

And there is no direct correlation between DNS functioning and throughput speeds.

Potential DNS issues can not affect the speeds you see reported at speed testing sites or the transfer rate of files.




Message Edited by EG on 07-09-2008 06:11 PM


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Problem Solver
Moved:

Re: How to Flush your local DNS cache

Post about poor connection speed moved to Internet Connection Forum. DNS flushing is not a connection speed remedy.