[plug] Re: Bind Question

[Matt Kemner]

On Fri, 22 Jul 2005, quoth Mark B:

>     every zone MUST have a different unique serial number, the serial number
> can be anything numerical.  make sure you are not just simply coping the
> zone file from another zone.

Sorry, but this is incorrect.

The serial number is used by slave DNS servers to figure out if a zone has
changed.  It is not used to differentiate one zone from another.

Every time you make a change to your zone (on your master DNS server) you
need to increment the serial number.  The slave servers regularly[0]
request the serial number from the master, and if they detect it has
changed they will request a zone transfer to get the up-to-date zone.

General convention is to specify the serial number as the date of the last
change followed by two numbers - to allow for multiple updates in a single
day.  Eg. zones changed today would have the serial number of 2005072200
however there's nothing stopping you from starting at 1 and working your
way up.

It is perfectly legal to have multiple zones with the same serial number
(handy when doing mass updates with sed(1) or perl(1)) the only rule is
that the number must always go up.

 - Matt

[0] You can also specify how often the slave servers check for the serial
    number, with the number that follows the serial number (Refresh)
    These days it is more common to use the "NOTIFY" system, where the
    master server tells the slaves the zone has been updated.
    They will still check the serial number, so you must make sure to
    always increment it.