IXFR and AXFR

[p...@mail.nsbeta.info]

At what time the slave executes AXFR and at what time it executes IXFR from
the master?

Thanks.

[Eivind Olsen]

> At what time the slave executes AXFR and at what time it executes IXFR
> from the master?

Someone please correct me if I give misleading information. I don't
believe I am, but I've been wrong before :D

There's a good section about this in the ARM, such as BIND 9.7 ARM section
4.3 - Incremental Zone Transfers (IXFR).

Basically, a BIND 9 slave will normally ask for IXFR unless told not to
(request-ixfr).
A BIND 9 master can't always provide IXFR though - if it can't it will
provide AXFR instead. To be able to provide IXFR it needs to have some
idea of the changes being made, so it can give a meaningful reply when
asked to provide "all changes since serial number X", so you'll normally
see IXFR being possible for dynamically updated zones (and a couple of
other cases, check the ARM).

Regards
Eivind Olsen

[Mark Andrews]

In message <e39f60e8c9db5f989a36...@webmail.aminor.no>, "Eivind Ols

named will do a axfr initially, anytime it believes it has lost sync with the
master (the ixfr did not apply without error), when "rndc retransfer" is
called, when ixfr is rejected by the master.

The master will return a AXFR style IXFR whenever it doesn't have the requested
axfr stream.

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Mark Andrews, ISC
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[p...@mail.nsbeta.info]

Mark Andrews writes:

> The master will return a AXFR style IXFR whenever it doesn't have the requested axfr stream.

Do you mean whenever it doesn't have the requested IXFR stream?

Thanks.

[Mark Andrews]

When you make a IXFR request you say "please send me the changes starting at
this serial". Sometimes the master will have already discarded some or all
of the changes. IXFR allows for optional compression of deltas and if one of
the masters in the axfr graph does that and you have multiple masters listed
you make end up ask a master that about a serial that was compressed away.

> Thanks.