Clear DNS cache

How can I clear the DNS cache?
When I configure my webserver and change the records, I have to wait the time configured in the ttl of the specific record. I know, that I can change the ttl to a lower value, but the default value is 3 hours, so i have to wait until the time's up.
I checked the DNS records with dig (from dnsutils). dig also shows the remaining seconds until the next refresh (dns server request). And here's my question: How can I refresh it manually? (tried a lot from the internet, but nothing helped)
Thank you guys!
Last edited by gummiflummi (2014-12-16 20:41:53)

brebs wrote:Woah right there. Why do you need to *change* the records? Shouldn't happen often.
Other than the answer stated (to test DNS settings), you might want to change records for a (self-hosted) DynDNS service. If you want a device to updated its DNS entries while being connected to a shaky cellular network, those changes might occur frequently with changing IPs.
To the original poster: You should always set the TTL to a reasonable setting. If you didn't change the record for the last two years, then maybe a TTL of several hours (or even a day) might be OK. If you want to be able to react more quickly to emergency situations, set it lower. For a DynDNS service, TTLs below a minute might be appropriate.
If you want to test your DNS Server, you can always query it directly (bypassing your ISP's DNS servers) with a command like this (where 1.2.3.4 is the IP of your nameserver):
dig @1.2.3.4 your.entry.example.com
This will usually show you the new settings right after changing.

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Clearing DNS cache dynamically

Can someone please guide me on how DNS cache dynamically. I have read about the networkaddress.cache.ttl settings but would like to know if there is some other way because changing ttl value would affect the other services deployed. I have searched a lot for this but without much luck.

Hello
I have exactly the same problem and it has really frustrated me, anybody else outside our house sees the right page except me!
I've read this thread and don't quite understand the solution. If I have to wait, how long do I need to wait for our router to see the same as the rest of the world
What do I need to do? Your help is really appreciated

What to do when clearing DNS cache fails?

dig {FQDN}
gives correct info from appropriate DNS server
ping {FQDN}
fails with wrong IP address, presumable cached from long ago. Flushing the cache is done differently on Lion (http://support.apple.com/kb/HT5343?viewlocale=en_US&locale=en_US):
sudo killall -HUP mDNSResponder
appears to succeed, but ping still fails with wrong IP address ...
{FQDN} is FQDN of Microsoft Active Directory domain, to which the Mac is bound, but DCs have changed & have different IP addresses now.
BTW - bug in Directory Utility on Mountain Lion - can`t get out of editing settings for directory without quitting entirely - is annoying.
Presumably unbinding the Mac from AD might help, but there doesn't seem to be an option to do this (and presumably will fail, since it can't contact the old DC?!)

Thanks. Spot on. Edited /private/etc/hosts with correct IP addresses of domain controllers against FQDN of AD domain. Required reboot in my case.

2008 R2 DNS does not resolve external websites until I clear DNS cache

Do I need to apply this hotfix
http://support.microsoft.com/kb/2508835/en-us
MCSE Certified

Thank you for posting the ipconfig /all, but we can't use it since the relevant data that we need to evaluate has been blocked out. I can understand if you have a strong security policy.
The Conditional Forwarders shouldn't be causing you to not to resolve specific domain names.
How long has this been going on?
What exactly occurs? Does DNS stops totally responding when you test it with nslookup, or are you just testing it with Internet Explorer?
If you have nslookup tests and responses, it may be helpful to see them, but if your security policy prevents you from posting them, I understand.
I'm curious about this part that you posted:
> "And as suggested by microsoft
> earlier,we have blocked few DNS
> Domains by creating conditional
> forwarders , pointing to
> our another domain."
Did you open a ticket with Microsoft support that provided this suggestion? If yes, you can email your support engineer that assisted you.
Or did you post this in this forum or elsewhere that you received this suggestion? If a forum post, do you have a link?
Without specifics, it may be difficult to assist. However, what I can provide are the following hotfixes. The second one you had already installed. I suggest and recommend to install the others.
1. DNS Server service does not use root hints to resolve external names in Windows Server 2008 R2
Post Windows 2008 R2 SP1 HOTFIX available.
APPLIES TO •Windows 2008 R2 Datacenter •Windows 2008 R2 Ent •Windows 2008 R2 Std.
Requires a restart.
http://support.microsoft.com/kb/2616776
2. DNS Server service does not resolve some external DNS names after it works for a while in Windows Server 2008 R2
Hotfix release - (released 4/15/2011)
http://support.microsoft.com/kb/2508835
3. Windows 2008 -
DNS queries for external domains are not resolved when you use Conditional Forwarding in Windows Server 2008
Post Windows 2008 SP2 Hotfix available
Requires a restart.
http://support.microsoft.com/kb/2625735/
4. DNS server stops responding to DNS queries from client computers in in Windows Server 2003, in Windows Server 2008 or in Windows Server 2008 R2 - Post Service Pack Hotfix available.
Does not require a restart.
http://support.microsoft.com/kb/2655960
If the above do not help or provide improvements, I highly suggest to contact Microsoft Support for specific assistance. Here's the link if you decide that you need to go with this option:
http://support.microsoft.com/contactus/
Ace Fekay
MVP, MCT, MCSE 2012, MCITP EA & MCTS Windows 2008/R2, Exchange 2013, 2010 EA & 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP - Directory Services
Complete List of Technical Blogs: http://www.delawarecountycomputerconsulting.com/technicalblogs.php
This posting is provided AS-IS with no warranties or guarantees and confers no rights.

I cannot clear DNS Cache on Imac OS 10.9

If I type this in the terminal...dscacheutil -flishcache;killall -HUP mDNSResponder
it ask for admin password but i cannot type that
Somebody that can help

Hi RJSomps,
When you type the password into the Terminal application in order to execute a command, the actual password does not appear while typing it. This is a security feature. See this article for details.
Mac OS X: sudo command requires a non-blank admin password
http://support.apple.com/kb/HT4103
Specifically -
When typing the user's password after the "Password:" prompt appears, you will not see anything appear in the Terminal window. Just type in the password and press Return. If the password is entered incorrectly, you will see the message "Sorry, try again" and be given another chance to enter the password correctly.
Thanks for using Apple Support Communities.
Best,
Brett L

I cant download new iphone update. i have turned off firewalls disabled security cleared dns cache and still nothing. i get this message err = _3259.

i get this as a pop up message also
There was a problem downloading the software for the iphone xxxx. The network connection timed out.
Make sure your network settings are correct and your network connection is active, or try again later.
im stil on O.S. 4.3.2 as this was the last one i have been able to update to. Please help=)

try taking Thunderbird offline File menu (Alt+F) > offline > workoffline
Close Thunderbird
reboot your computer
Restart Thunderbird and try compacting while Thunderbird is still offline.

Export DNS cache

After searching around, I've found a ton of posts about clearing DNS Cache, but what I'm actually looking for is a way to export the DNS cache out of bind to some sort of text file. Basically, I'm hoping to build a static dns cache lookup file to use with AWStats, and wanted to see if it was worthwhile using entries from the several DNS servers we having running.

Hi Alex
rndc dumpdb should do.
Regards
--greg

Solaris dns cache

HI;
Will this command "kill `cat /var/named/named.pid`" clear the dns cache or just disable named pid and when it`s going to be reload again will continue as it was before?

kill the named ( dns ) process i usually used pkill named
and start it again should clear dns cache , also i restart nscd ( name serivice cache daemon if doesnt help by /etc/init.d/nscd stop & /etc/init.d/nscd start
Regards

How can I clear the DNS cache?

I haven't been able to connect to my local Library since January. When I key in the URL, it starts the access routine and then after about 20 minutes, I have to kill it because nothing happens. I contacted the IT folks at the library and was told that they had made a few changes around the time my problem began so maybe the DNS cache was still pointing at the old info. He recommended that I enter TERMINAL mode and try to clear the DNS cache, using "sudo dscacheutil -flushcache" command. . I attempted this several times, even changing my applid password, and kept getting invalid responses.

I did try that and after a few trys it finally worked. It took quite awhile for the window for the library to finally come up, but it did and I am now able to get in and out with no problems with my library access. Now when I call up my bank, parts of it don't come up and it kicks me out. Now, I'll have to search for what fixes that - as it has happened before, so I know it's fixable. Thanks for you help though.

Where Is My DNS Cache And How Do I Clear It?

I'm using Timbuktu to reach my desktop iMac remotely. I subscribe to DYNDNS to detect IP changes. Recently, after a blackout, I could not reach the iMac remotely via DYNDNS. I WAS able to use the new IP (which I had someone look up for me) and Timbuktu connected just fine.
After contacting DYNDNS, they told me to clear my DNS cache, as that was probably the reason why their detecting system could not see the new IP.
My head is spinning. Can some kindly tell me where the DNS cache is on my iMac 10.4.11 and how to clear it? (For idiots, please).
Many thanks
---Gary

Yes, it's clear. Thanks.
I'm just too nervous to try this until my Mac Guru is sitting here. I can't unscramble anything I screw up...and that's a pretty good possibility based on past events.
Again, thanks
Gary

HT5343 Why is killing mDNSResponder the recommended method of clearing your DNS cache in 10.7+?

mDNSResponder is also in control of Bonjour advertisement and unicast DNS resolution. So killing mDNSResponder is a good way to clear your cache in the same way that throwing your computer out a window is a good way to turn it off.
Why not continue to use "sudo dscacheutil -flushcache" like we always have? It still even works in 10.7+.

As Linc indicated, the command recommended by Apple is:
sudo killall -HUP mDNSResponder
This restarts the process; it doesn't kill it. In 10.7 and 10.8 the mDNSResponder daemon caches DNS query results, so even if you flush the other cache, old results can still crop up. Restarting the mDNSResponder daemon clears that cache.
Regards.

Yosemite 10.10.1 - DNS cache does not clear when switching between WiFi networks

Before updating to Yosemite, DNS caches would clear when switching between WiFi networks, as they should.
For Example, when using an Exchange server, your server name might be something like mail.company.com. Outside of the corporate LAN the IP would resolve to the outside (WAN) address. When you move the laptop inside the corporate LAN, it should clear the cache so mail.company.com resolves to the internal (LAN) address. This is just one example of a dumb DNS transition not taking place switching from outside to inside (and vice versa).
Instead, OS X is holding onto the outside DNS record even when moving to the Corporate LAN. The only way to fix is to run the DNS cache command (which is MUCH more convoluted in Yosemite now), or more easily, to quickly turn off then turn on WiFi.
This is an irritation as I have to perform this action every morning, and every time I come back to my desk from offsite.

Well, clearing the caches is as simple as this, no?
Clear MDNS Cache
sudo discoveryutil mdnsflushcache
Clear UDNS Cache
sudo discoveryutil udnsflushcaches
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Possible DNS caching problem

I just upgraded to Lion. I am a web deveoper and I just changed the DNS settings for a new website. While everyone else in my office is seeing the new wesite at the domain, I am stuck seeing the old. I have tried the DNS cache flushing techniques below (in addition to restarting, clearing cache, etc), but none have helped:
sudo killall -HUP mDNSResponder
dscachutil -flushcache
In the terminal 'host domain.com' still points to the old server too.
Seems like OSX is holding on to the old DNS settings. Any ideas?

Select  ▹ System Preferences ▹ Network ▹ Advanced ▹ Proxies. If any boxes are checked, uncheck them, apply your changes, and try again. You must apply the changes before they take effect.

DNS Cache Failure

I'm having a problem with my Mac and DNS and it is related to http://discussions.apple.com/thread.jspa?threadID=2132856&start=0&tstart=0 however no one seems to have come up with an actual solution and I've got the problem pretty much narrowed down here.
So, the mac is all set up properly and can connect to the internet fine, however, DNS lookup fails the SECOND time I do a lookup. i.e.,
*> ping google.com*
*PINGING blah blah all ok*
*> ping google.com*
*ping: cannot resolve: unknown host*
Clearing the cache resolves this problem for one lookup:
*> ping google.com*
*PINGING blah blah all ok*
*> ping google.com*
*ping: cannot resolve: unknown host*
*> dscacheutil -flushcache*
*> ping google.com*
*PINGING blah blah all ok*
*> ping google.com*
*ping: cannot resolve: unknown host*
Accordingly, nslookup always works as it does not use the local cache.
Now, I've checked all the usual solutions: router config, dns config, router vs. direct connect, type and number of dns servers, resolve.conf, etc., etc. and cannot come up with a solution.
Surely there is a fix to this someone is aware of? +Or, if not, is there at least a way to disable local DNS caching?+

Yes, I have already looked into that.
I've tried it with one DNS and multiple DNS, both with various combinations of open DNS servers and my ISP's servers and the default router "server" and in the various orderings and options in resolv.conf. And I checked the various man pages to make sure I was covering all the options and it looks like I was.
In all cases the problem behaves exactly the same.
FWIW I have 3 windows machines, 1 Mac 10.2, 1 Mac 10, and a linux box on my network, and they all work fine with no special configuration (DHCP). Seems particular to 10.6 (well, 10.3+ at least, though I would assume it has to do with the DNS change in 10.6 from 10.5).
Message was edited by: squirlhntr

Wie kann ich den DNS Cache zurücksetzen?

Wie kann ich den DNS Cache bei OS X Mavericks (10.9) zurücksetzen?

Deleting the full cache folder (_CACHE_* files and all subdirectories) in the location as found via about:cache should normally work without problems provided that Firefox isn't running when you delete the files.<br />
You may have to delete the _CACHE_CLEAN_ file in the parent location as well.
What kind of problems do you get if you delete the Cache folder?
Note that Firefox wouldn't use the disk cache if you use "Clear history when Firefox closes" to clear the cache as you can see on the about:cache page, so you would have to clear the cache manually in Firefox.

Clear DNS cache

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