Re: [PLUG] dns propogation

["Michael C. Toren" <mct@toren.net>]

> I do run a dns server (bind 9), I'm not expert on it, but I was
> thinking I could set the time to live to 0 for the time being.
> Problem is that ttl is specified in a few spots, and I don't know
> which one is for which, part of the file looks something like:

> $TTL 3D

For modern day versions of bind, the above line is the value you'd want
to change in order to set the default TTL.  I would personally recommend
a value of 10 minutes or so, rather than zero.

> There is a ttl up top, and a bunch in the SOA.

There are a number of values in the SOA record, but they don't all have
to do with the TTL.  You have:

>                                 1       ; Serial

The serial number.  If you have any secondary nameservers pulling a copy
of this zone from you (you should have at least one), the secondary will
only pull a new copy if the serial number on the primary is greater than
the serial on the secondary, which means you'll need to increment it each
time you modify the zonefile.  Many people like to use the current date,
in the format YYYYMMDDnn, for the new serial numbers.

>                                 8H      ; Refresh

The refresh value determines how often a secondary will query the primary
to see if the serial number has been incremented.

>                                 2H      ; Retry

If a secondary wasn't able to query the primary's serial number, it will
wait this long before trying again.  Typical retry values are either half,
or a quarter of the refresh time.

>                                 4W      ; Expire

If a secondary isn't able to query the primary's serial number after this
long, it will discard any data which it may have previously retrieved from
the primary, for fear that it's so horribly out of date it isn't worth
redistributing.

For more information, I would suggesting reading through the DNS HOWTO,
which appears to be available at <http://langfeldt.net/DNS-HOWTO/>.

HTH,
-mct