how to check if a slave zone is expired

[Chris Thompson]

On May 4 2011, Doug Barton wrote:

>On 05/04/2011 01:22, hugo hugoo wrote:
>> So..no way to check that a zone is expired?
>
>You're asking the wrong question. The correct question is, "How can I 
>make sure that a zone is up to date on all of the slaves?" You do that 
>by querying the SOA record for the zone on each slave and compare the 
>serial number to the master.

This isn't necessarily the "right question". It is perfectly possible
for a slave's copy of a zone to be up to date, but still be about to
expire, because the slave has been unable to *confirm* that it is up
to date for the expiry period (due to network problems, configuration
errors, or whatever).

If Mark Andrews' "EDNS Expire Option" I-D had taken off, one would be
able to use that to test time-to-expiry for a zone from outside the
server, rather than messing about with the modification times of the
master files. But sadly, it didn't ...

-- 
Chris Thompson
Email: cet1 at cam.ac.uk