It *shouldn't* ever be necessary to flush this cache. An exception might
be if you determined that your machine had received "tainted" DNS
information from a compromised server, and had re-pointed it to a known good
server, but that should be a very rare occurrence.
As far as I know, the cache lives in RAM belonging to the network
components of the OS, and will be discarded by a reboot.
The normal order of resolution should be something like:
1. Check the cache to see if this name has already been resolved recently.
2. Check the hosts file in case we've been manually given a resolution to
use.
3. Ask the primary DNS server to resolve the name.
4. Ask the secondary DNS server. (Note that at least on some versions, the
whole resolution process may time out and fail before or at this point.)
I have seen some weird states: where IE and/or Outlook could resolve, but
no other applications could -- or vice versa! We had a machine a few days
ago that wasn't resolving because it was sending DNS names to a WINS server
instead of the DNS server. I believe a reboot has been known to clear all
of these.
David Gillett
On 22 Dec 2006 at 23:26, Don Penlington wrote:
Date sent: Fri, 22 Dec 2006 23:26:37 +1000
Send reply to: PCSOFT - Personal Computer software discussion list
<[log in to unmask]>
From: Don Penlington <[log in to unmask]>
Subject: [PCSOFT] Flush DNS cache
To: [log in to unmask]
> When I run Ipconfig with the flushdns command, I get an error message
> "Function failed". Same thing happens when I try to run a repair on the
> ADSL modem.
>
> What would be the reason for this failure?. I have normal sole user Admin
> rights. Can I open the DNS cache manually--if so, where is it? Could some
> security setting/protection software be blocking it? I've a vague idea the
> hosts file is locked (by Zone Alarm I think)---could this be the reason?
>
> XP Pro SP2.
>
> It doesn't seem to be causing any problems---yet. Might this failure be
> important in the future? Is it good practice to flush this cache regularly?
>
> Don Penlington
> From the Beach at Surfers Paradise in sunny Queensland.
> Computer tutorials, local scenery, and other things at my website:
> http://users.tpg.com.au/deepend/index1.html
>
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