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Old 01-20-2009, 08:13 PM
"Naju ...."
 
Default DNS Communication

Hi,

AFAIK, a dns master server will not send any notifications to slaves. A
slave server lookup for an updated zone data according to it's refresh time
( mentioned in SOA). When a slave contacts master for a zone data, it first
ask for the serial number on the data, if the slave's serial number for this
zone is lower than the master's, then slave's zone data is out of date. So
slave pulls a new copy of zone( an AXFR transfer).

Whenever you update the master's database, you should bumb the serial number
as well.

On Wed, Jan 21, 2009 at 1:23 AM, Giuseppe Fuggiano <
giuseppe.fuggiano@gmail.com> wrote:

> Hi all.
>
> Given two DNS servers, one master and one slave, I'd like to
> understand what exactly happens when I update the database of the
> first one.
>
> What I know is that the first one, if properly configured, sends a
> NOTIFY message to its slave and the slave replies. What happens then?
> How the slave update its database?
>
> Good links are also welcome. Thanks.
>
> --
> Giuseppe Fuggiano
>
> --
> redhat-list mailing list
> unsubscribe mailto:redhat-list-request@redhat.com?subject=unsubscribe
> https://www.redhat.com/mailman/listinfo/redhat-list
>



--
Cheers
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Old 01-20-2009, 10:53 PM
"Gardiner, James"
 
Default DNS Communication

>>"a dns master server will not send any notifications to slaves."

Sorry NAJU this is absolutely wrong.
BIND Servers by default DO send NOTIFY primitives to all slaves NameServers listed as NS records for a zone, whenever the zone is loaded or reloaded with a higher serial number.
The NOTIFY message will trigger the slave to send an SOA request to the Master, and an XFER will start if the serial number is higher. In effect it shortcuts the refresh time countdown. This behavior can be turned off with the 'notify no' directive in named.conf.

Microsoft DNS servers may not notify by default, but this behavior can be enabled. Here is a Wuote from a very reliable source describing this:

"There's actually a window the administrators of your Microsoft DNS Servers should check to make sure they've configured NOTIFY correctly. They need to highlight the domain name of a zone in the admin interface, select Action->Properties, then choose the Zone Transfers tab of the zone properties window. Then select the Notify... button and make sure :Automatically notify:" is checked. If it's checked, either "Servers listed on the Name Servers tab" should be checked, and the name server you want notified should be listed on that tab, or "The following servers" should be checked, and your name server's IP address should be listed, along with the others you want notified, in the list box below."

This can be found here:http://dig.menandmice.com/knowledgehub/dnsqa/6

AFAIK I hope this answers your question.

JG



-----Original Message-----
From: redhat-list-bounces@redhat.com [mailto:redhat-list-bounces@redhat.com] On Behalf Of Naju ....
Sent: Wednesday, 21 January 2009 8:13 AM
To: General Red Hat Linux discussion list
Subject: Re: DNS Communication

Hi,

AFAIK, a dns master server will not send any notifications to slaves. A slave server lookup for an updated zone data according to it's refresh time ( mentioned in SOA). When a slave contacts master for a zone data, it first ask for the serial number on the data, if the slave's serial number for this zone is lower than the master's, then slave's zone data is out of date. So slave pulls a new copy of zone( an AXFR transfer).

Whenever you update the master's database, you should bumb the serial number as well.

On Wed, Jan 21, 2009 at 1:23 AM, Giuseppe Fuggiano < giuseppe.fuggiano@gmail.com> wrote:

> Hi all.
>
> Given two DNS servers, one master and one slave, I'd like to
> understand what exactly happens when I update the database of the
> first one.
>
> What I know is that the first one, if properly configured, sends a
> NOTIFY message to its slave and the slave replies. What happens then?
> How the slave update its database?
>
> Good links are also welcome. Thanks.
>
> --
> Giuseppe Fuggiano
>
> --
> redhat-list mailing list
> unsubscribe mailto:redhat-list-request@redhat.com?subject=unsubscribe
> https://www.redhat.com/mailman/listinfo/redhat-list
>



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Old 01-21-2009, 07:51 AM
Giuseppe Fuggiano
 
Default DNS Communication

2009/1/21 Gardiner, James <James.Gardiner@det.nsw.edu.au>:
> The NOTIFY message will trigger the slave to send an SOA request to the Master, and an XFER will start if the serial number is higher. In effect it shortcuts the refresh time countdown. This behavior can be turned off with the 'notify no' directive in named.conf.

Specifically, my question is:

Does the slave connect to the master, or viceversa (when either the
timeout or a NOTIFY message is triggered)? Which protocol is used for
that connection?

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Old 01-22-2009, 01:31 AM
"Gardiner, James"
 
Default DNS Communication

The slave contacts the master.

In detail:

Master sends a NOTIFY to the slaves (Identified by NS records) The Notify looks much like an SOA query except it has a different Opcode set in the packet header (NOTIFY instead of QUERY).

Upon receipt of the NOTIFY announcement the slave replies with a NOTIFY response (to stop the master sending more NOTIFY announcements).

The slave then proceeds with a normal SOA request just as if the refresh time has counted to 0.
It is a standard UDP port 53 SOA Query, which is answerred with the SOA RSP.

Assuming the serial number in the newly received SOA is greater than the one the slave has, the slave will start a zone transfer (AXFR or IXFR Request).
Note that zone tranfers are done as a TCP (not UDP) port 53 transaction, with the slave as the initiator and the master as the responder. This is because zone transfers do not need to be fast (and they are not, by FTP standards!) but need to be reliable (which they usually are).

Is that what you meant by which protocol?

J



-----Original Message-----
From: redhat-list-bounces@redhat.com [mailto:redhat-list-bounces@redhat.com] On Behalf Of Giuseppe Fuggiano
Sent: Wednesday, 21 January 2009 7:51 PM
To: General Red Hat Linux discussion list
Subject: Re: DNS Communication

2009/1/21 Gardiner, James <James.Gardiner@det.nsw.edu.au>:
> The NOTIFY message will trigger the slave to send an SOA request to the Master, and an XFER will start if the serial number is higher. In effect it shortcuts the refresh time countdown. This behavior can be turned off with the 'notify no' directive in named.conf.

Specifically, my question is:

Does the slave connect to the master, or viceversa (when either the timeout or a NOTIFY message is triggered)? Which protocol is used for that connection?

--
Giuseppe Fuggiano

--
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unsubscribe mailto:redhat-list-request@redhat.com?subject=unsubscribe
https://www.redhat.com/mailman/listinfo/redhat-list
************************************************** ********************
This message is intended for the addressee named and may contain
privileged information or confidential information or both. If you
are not the intended recipient please delete it and notify the sender.
************************************************** ********************

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Old 01-22-2009, 07:20 AM
Giuseppe Fuggiano
 
Default DNS Communication

2009/1/22 Gardiner, James <James.Gardiner@det.nsw.edu.au>:
> Is that what you meant by which protocol?

Yes, you have been very clear. Thank you very much!

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