Refreshing cache in other DNS servers

[Kevin Darcy]

There's no way within the DNS protocol itself to reach out and tell a 
nameserver to purge an entry in its cache that hasn't expired yet.

There are "out of band" ways: e.g. restart, recycle, rndc commands, etc. 
All of those require admin access to the nameserver instances in 
question. But nothing within the DNS protocol itself allows one to do this.

That's why everyone is saying you need to reduce the TTL value *before* 
you make a change, if you want that change to be visible quickly.

                             - Kevin

On 10/15/2013 10:53 AM, babu dheen wrote:
> Hi Matus,
> /"The standard way to handle this situation is, when you know you are 
> going to
> make a change, to lower TTL of a particular RR to a small value (e.g.  
> 300)
> and after change to restore the TTL to sane standard value (e.g.  
> 43200)."/
> //
> /I just need clarification on your above update./
> //
> / If I change the TTL value on the particular zone after modifying a 
>  record in Redhat Linux BIND Caching DNS server, My Redhat bind 
> Caching DNS server cache would be refreshed after 300 seconds but what 
> if my backend windows  DNS server is still responding to  end user old 
> record from  from its cache?/
> //
> //
> /So my backend windows DNS server can get the newly modified record 
> from DNS only when its contacting Redhat DNS server for the newly 
> added date once Windows DNS cache is refreshed?/
> //
> /Regards/
> /Babu/
> //
>
>
> On Tuesday, 15 October 2013 3:04 PM, Matus UHLAR - fantomas 
> <uhlar at fantomas.sk> wrote:
> On 15.10.13 19:38, babu dheen wrote:
> > I am running BIND caching DNS server in Redhat Linux. This DNS server is
> >used as name server for other DNS servers which are running in Windows
> >2003.  Whenever I modify a existing record in BIND DNS caching server 
> zone,
> >its not immediately taking affect in my Windows DNS servers.  But if I
> >clear the Windows DNS server DNS cache, its taking affect.
>
> > Is it possible to enforce/refresh cache of other DNS server through BIND
> > DNS server once modification is done in zone file?
>
> No. Only server admins can maintain caches.
>
> Your job is to set TTL high enough not to cause you big load and not 
> to time
> out when your servers fail, but low enough to refresah when needed.
>
> The standard way to handle this situation is, when you know you are 
> going to
> make a change, to lower TTL of a particular RR to a small value (e.g.  
> 300)
> and after change to restore the TTL to sane standard value (e.g.  43200).
>
> You may ask for access to win2003 servers to manipulate their caches, or
> configure your zone as slave on them and send notifies to them, so they
> notice as soon as possible.
>
> -- 
> Matus UHLAR - fantomas, uhlar at fantomas.sk ; http://www.fantomas.sk/
> Warning: I wish NOT to receive e-mail advertising to this address.
> Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
> 2B|!2B, that's a question!
>
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