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beer9Flag for India

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How IXFR works with BIND name server?

I understand that IXFR sends the 'incremental' record since the last update. I would like to know how BIND get to know the difference of last and current and then send only the difference? Appreciate any leads here

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The description of IXFR is in:   (RFC 1995)

And it consists of Notification to specified slave-zones on updates (which contains the SOA version number)
the slave zone then does a bulk transfer over TCP/IP if the version on the slave is lower then the one in the notification.
Normal transfer is full transfer, i.e. AXFR
IXFR needs server which is already slave server and calculates incremental updates (aka journals) between zone versions sent by (isolated) zone master server. Master server alone cannot generate them.
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So BIND master server keep journal of every update (difference) since the last update to it's zone fine? How it works?

I will edit the zone file manually (using VIM) then before saving and closing I will increment the serial number by 1. Then I will reload/restart the BIND service. How it will track the differences ?
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For dynamic zones - yes, master server has journal.
For static zones (most common setup) - you need an interim server to calculate differences.
I can agree to that.