Caching-Only server TTL

  • Thread starter Thread starter Hooty
  • Start date Start date
H

Hooty

What is the TTL for forward lookups cached by a Caching-
Only server? (DNS installed, configured to forward, no
local zones) Can it be adjusted? I know it can be
manually cleared via "dnscmd /clearcache" or via the MMC.
I would rather have it maintain itself.

Thanks much in advance
 
H> What is the TTL for forward lookups cached by a Caching-Only server?

How long is a piece of string ?
 
In
Hooty said:
What is the TTL for forward lookups cached by a Caching-
Only server? (DNS installed, configured to forward, no
local zones) Can it be adjusted? I know it can be
manually cleared via "dnscmd /clearcache" or via the MMC.
I would rather have it maintain itself.

Thanks much in advance
Click to expand...

It depends on the record itself wherever the record came from. Each zone
have configuration specifics, such as the TTL for records, so it's zone
specific. The max a W2k DNS will cache it, however, (if I remember right), I
believe is 7 days, to avoid some admins who put, for example, a 60 year TTL
on it, which we both know would be nuts, but that's why it limits it.

--
Regards,
Ace

Please direct all replies to the newsgroup so all can benefit.

Ace Fekay, MCSE 2000, MCSE+I, MCSA, MCT, MVP
Microsoft Windows MVP - Active Directory
 
AF> The max a W2k DNS will cache it, however, (if I remember right),
AF> I believe is 7 days, to avoid some admins who put, for example,
AF> a 60 year TTL on it, which we both know would be nuts, but
AF> that's why it limits it.

7 days for ISC's BIND and Dan Bernstein's "dnscache".
1 day for Microsoft's DNS server.
 
In
Jonathan de Boyne Pollard said:
h> I guess my "string" is 1 day "long"!!!

No. As Ace said, that's the _maximum_ length that your string _could
be_.
Click to expand...

True.

Hooty, what's ther zone's TTL?


--
Regards,
Ace

Please direct all replies to the newsgroup so all can benefit.

Ace Fekay, MCSE 2000, MCSE+I, MCSA, MCT, MVP
Microsoft Windows MVP - Active Directory
 
In
hooty said:
Thank you both for your continued help.

The zone that the system is in has TTLs of 1 day or less
for all records. I wasn't really worried about local
stuff. I was more concerned with external records.
Click to expand...

As we both said, the record on a TTL has to deal with any server that gets
an answer and will store it for that long, unless the record is beyond the
Max TTL of the server.

I
think I should have asked if there was a Maximum TTL for
the records that are cached. In general, if MS-DNS will
use a self imposed maximum of 1 day then I don't have to
worry about it caching records whose owners decided to use
longer ones.

The system is going to be a multi-function box at a remote
site over a SLOW link that is their only connection to the
internet. They also get e-mail, database and uncommon
shared files over the line. I'm just trying to reduce the
duplicate traffic on the pipe. 1 day max is good and
tells me that I won't need to schedule a script to clean
it for where it is going.

Is there a registry key that defines the max TTL for the
server? I know there is one for the client resolver.

Thanks
Click to expand...

All of the DNS parameters are registry values located under subkeys of:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\parameters
MaxCacheTtl
Value: MaxCacheTtlType: DWORD
Default: NoKey (Cache for up to one day)
Function: Set maximum caching TTL.
-- Regards,AcePlease direct all replies to the newsgroup so all can
benefit.Ace Fekay, MCSE 2000, MCSE+I, MCSA, MCT, MVPMicrosoft Windows MVP -
Active Directory-- =================================
 
h> I'm just trying to reduce the duplicate traffic on the pipe.

Then a far bigger worry will be HTTP traffic. DNS traffic is paltry
by comparison. Set up a caching proxy HTTP server on the end of the
pipe nearest to them, and have them use it.

h> 1 day max is good and tells me that I won't need to
h> schedule a script to clean it for where it is going.

Why would you want to, given your stated goal ? Expiring any resource
records after a maximum of 1 day _increases_ DNS traffic.

h> Is there a registry key that defines the max TTL for the
h> server?

Yes.

<URL:http://support.microsoft.com./support/kb/articles/Q198/4/08.ASP>
 
Thank you, you've been a great help.
-----Original Message-----
In hooty <[email protected]> posted his concerns then I replied down below:

As we both said, the record on a TTL has to deal with any server that gets
an answer and will store it for that long, unless the record is beyond the
Max TTL of the server.



All of the DNS parameters are registry values located under subkeys of:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\pa
rameters
MaxCacheTtl
Value: MaxCacheTtlType: DWORD
Default: NoKey (Cache for up to one day)
Function: Set maximum caching TTL.
-- Regards,AcePlease
Click to expand...
direct all replies to the newsgroup so all can
 
In
hooty said:
Thank you, you've been a great help.
Click to expand...

No prob.
:-)
--
Regards,
Ace

Please direct all replies to the newsgroup so all can benefit.

Ace Fekay, MCSE 2000, MCSE+I, MCSA, MCT, MVP
Microsoft Windows MVP - Active Directory
 
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