How IXFR works with BIND name server?

beer9
beer9 used Ask the Experts™
on
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

Thanks!
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nociSoftware Engineer
Distinguished Expert 2018

Commented:
The description of IXFR is in: https://tools.ietf.org/html/rfc1995   (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.
Top Expert 2015

Commented:
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.

Author

Commented:
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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Software Engineer
Distinguished Expert 2018
Commented:
If you DO Please FIRST FREEZE the zone..., so the journal gets comitted to the zone file, then edit the zone file, Then THAW the zone..

rndc freeze my.example.com
$EDITOR my.example.com.zone
rndc thaw my.example.com
Top Expert 2015

Commented:
For dynamic zones - yes, master server has journal.
For static zones (most common setup) - you need an interim server to calculate differences.
nociSoftware Engineer
Distinguished Expert 2018

Commented:
I can agree to that.

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