Significance of @ symbol in soa record.
DougB at DougBarton.net
Sat Jan 11 03:43:20 UTC 2003
On Fri, 10 Jan 2003, colors wrote:
> I am trying to learn about the significance of the '@' symbol at the start
> of the line where the soa record is contained.
The @ symbol, wherever it appears in a zone file, stands for "the current
$ORIGIN." At the top of the zone, the $ORIGIN is set to whatever zone name
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 zone
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.
> I am also wondering why one might want to have a ttl for a zone's soa record
> set at 60 seconds..?
Do you mean the ttl for the SOA record, or do you mean the last field OF
the SOA record, which is defined by RFC 2038 to be (roughly) "the length
of time to cache negative answers for this zone." If you mean the latter,
then 60 seconds is a reasonable time period, since you don't want remote
resolvers constantly re-querying for a record that doesn't exist, but you
don't want to prevent them from seeing something for a long time after you
Hope this helps,
PS, you should really go buy "DNS and BIND, Fourth Edition" and read it.
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