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How often does the DNS cache clear on a Windows 7 machine?

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3 Answers 3

up vote 17 down vote accepted

The DNS cache doesn't ever flush, unless you explicitly tell it to or you make a DNS/networking related configuration change. DNS records have a Time To Live (TTL) value associated with them which tells a DNS cache how long the particular record is good for. Records in the cache are kept for their TTL, then re-queried.

On a Windows machine you can see a list of all the records in your cache along with their TTL by executing the following command at the command prompt:

ipconfig /displaydns

You can force a flush of all cached DNS records using the following command:

ipconfig /flushdns

For more info:

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Thanks for the great answer mate! –  Harry Dec 9 '09 at 7:08
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From what I've been able to find, Windows 7 does not set a parameter for dnscache MaxCacheEntryTtlLimit.

The default value for MaxCacheEntryTtlLimit is DWORD = 0x15180 = 86400 seconds = 1 day

  • if DNS zone TTL < MaxCacheEntryTtlLimit, then DNS TTL is used
  • if DNS zone TTL > MaxCacheEntryTtlLimit, then MaxCacheEntryTtlLimit is used
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According to: Reduce DNS Client Cache in Windows Server 2012 R2

Instead of MaxCacheEntryTtlLimit you should modify maxcacheTTL. It works for Windows 8 too.

Description

Determines how long the Domain Name System (DNS) server can save a record of a recursive name query.

If the value of this entry is 0x0, the DNS server does not save any records.

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Thanks! Exactly what I was looking for. One more thing to add from that blog post run net stop dnscache & net start dnscache to make setting take without rebooting. –  Lucas Jul 11 at 9:50
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