Significance of @ symbol in soa record.

[phn at icke-reklam.ipsec.nu]

colors <btb at bitrate.net> wrote:

> On 2003.01.10 22.54, in article avo4ia$en1j$1 at isrv4.isc.org, "Doug Barto=
n"
> <DougB at DougBarton.net> wrote:

>>=20
>> On Fri, 10 Jan 2003, colors wrote:
>>=20
>>> I am trying to learn about the significance of the '@' symbol at the s=
tart
>>> of the line where the soa record is contained.
>>=20
>> The @ symbol, wherever it appears in a zone file, stands for "the curre=
nt
>> $ORIGIN." At the top of the zone, the $ORIGIN is set to whatever zone n=
ame
>> was given in the 'zone "name" ...' statement in the named.conf file.
>> Personally, I find it much less confusing to specify the name of the zo=
ne
>> in the SOA if I only have one zone per file. In a large scale operation=
,
>> this also helps flag errors when the wrong zone file is accidentally
>> referred to due to a typo in the conf file.
>>=20
>>> I am also wondering why one might want to have a ttl for a zone's soa =
record
>>> set at 60 seconds..?
>>=20
>> Do you mean the ttl for the SOA record, or do you mean the last field O=
F
>> the SOA record, which is defined by RFC 2038 to be (roughly) "the lengt=
h
>> of time to cache negative answers for this zone." If you mean the latte=
r,
>> then 60 seconds is a reasonable time period, since you don't want remot=
e
>> resolvers constantly re-querying for a record that doesn't exist, but y=
ou
>> don't want to prevent them from seeing something for a long time after =
you
>> add it.
>>=20
>> Hope this helps,
>>=20
>> Doug
>>=20
>> PS, you should really go buy "DNS and BIND, Fourth Edition" and read it=
.
>>=20
> Thanks everyone. I actually have dns and bind, 3rd edition, in which I
> originally had looked for example zone files where @ might be used - in
> fact, soa records in all of the examples in the book begin the the zone =
name
> spelled out, which gave me the impression that @ was equal to $ORIGIN, b=
ut I
> wanted to confirm.  Upon going back through the book, I did finally find
> mention of @ usage in the appendix.

> Regarding my second question, let me give an example to clarify:

> $TTL 1D
> @            60 in soa  ns1.1safari.com. hostmaster.ns1.1safari.com. (
>                         2003011000      ; serial
>                         12H             ; refresh
>                         30M             ; retry
>                         2W              ; expire
>                         1H )            ; negative caching

> I was referring the the value 60 preceding "in soa"

You dont want it. Remove it & life is better.

( what is says id that the SOA record ( and only that ) is only allowed
to be cached 60 seconds.

The contents in the zone may be cached 1 day ( $TTL 1D )=20
and negative answers ( there is no such thing) may be=20
cached 1 hour ( 1H )



> Thanks again
> -b


--=20
Peter H=E5kanson=20=20=20=20=20=20=20=20=20
        IPSec  Sverige      ( At Gothenburg Riverside )
           Sorry about my e-mail address, but i'm trying to keep spam out,
	   remove "icke-reklam" if you feel for mailing me. Thanx.