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Question
Tuesday, December 7, 2010 3:19 PM
Fairly acedemic question, but I can't seem to find a clear answer. I know that I can force cache to be cleared both on the client and the server but is there either a set time frame when cache becomes obsolete and thereby "cleared" at the server? ( Given it's a windows 2003 DNS server )
LMC
All replies (4)
Tuesday, December 7, 2010 6:46 PM ✅Answered | 1 vote
A DNS Server's cache is cleared at reboot. Other than that you can manually clear the cache at any time by using the DNS Admin console. If you leave the cache alone, the individual records are removed from the DNS cache as the TTL (time-to-live) expires.
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Tuesday, December 7, 2010 10:07 PM ✅Answered
I agree with JM.
You can view the TTLs in the DNS server cache by putting the View mode into Advanced View, then drill down to the cache, expand the related zone you want to look at, right click on a record, properties, you can see the TTL left in seconds. If you close it, then re-open the properties, you can see the TTL has lessened since the last time you opened the record properties.
Same on the client side. Run ipconfig /displaydns. You can see the cached items on the local client side cache. Hit arrow up and <enter> again to re-run the command and you can see the TTL counting down. Do it real quick and you can see it almost second for second.
THe TTL comes from the nameserver that hosts the Primary zone, or in an AD infrastructure using AD intergrated zones, the originating server where the record was created, which comes from the zone properties.
Ace
Ace Fekay
MVP, MCT, MCITP EA, MCTS Windows 2008 & Exchange 2007, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP - Directory Services
This posting is provided AS-IS with no warranties or guarantees and confers no rights.
Tuesday, January 28, 2014 11:59 PM
Is the cache cleared when the DNS Service is restarted?
thx!
Wednesday, January 29, 2014 3:55 AM
Is the cache cleared when the DNS Service is restarted?
thx!
Yes.
You can easily test it by following my post above using DNS console in Advanced View, look at the cache, then restart it, refresh the console and all the cached lookups disappear.
Ace Fekay
MVP, MCT, MCITP/EA, MCTS Windows 2008/R2 & Exchange 2007, Exchange 2010 EA, MCSE & MCSA 2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer
Microsoft MVP - Directory Services
Technical Blogs & Videos: http://www.delawarecountycomputerconsulting.com/
This post is provided AS-IS with no warranties or guarantees and confers no rights.