IN CNAME?

Re: IN CNAME?

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On 06/05/00 at 12:04, Men & Mice Support wrote:

> It occurs to me that my response was rather terse, explaining what to
> do without explaining why.
>
> There's a traditional DNS shortcut: Any name that doesn't end in a
> dot gets the origin string appended. The origin string in QuickDNS
> Pro is always the name of the zone. In BIND, the origin string is
> user-definable, but defaults to the name of the zone.
>
> The original point of this was, if you need to enter a large number
> of records by hand (especially if you don't have a mouse and don't
> have copy-and-paste), you don't want to have to retype the name of
> the domain for every record.
>
> The catch was, if you didn't know about the shortcut, you'd enter all
> your names without dots on the ends, and would end up with a bunch of
> garbage records. The data was entered in a text editor, which didn't
> know you were entering DNS records and didn't have any way to know
> what the origin string was. So you didn't know that everything was
> wrong until you actually queried your name server.
>
> With QuickDNS, we decided to use this traditional shortcut, because
> even with a mouse and copy-and-paste, it still makes sense. You enter
> "www" for "www.zone.name.". The difference is, with QuickDNS, you see
> the zone name appended right away (at least, if your columns are big
> enough).
>
> So anytime you want to enter a name that shouldn't have the zone name
> appended, end it with a dot.

Just to throw in a little further background, the trailing dot on a domain
name represents the 'root domain,' which is the parent of _all_ domains, and
the direct parent of the top-level domains (com, net, org, etc.). Technically,
a domain name that ends with a trailing dot (host.domain.com.) is an
'absolute' domain name, also referred to as a 'Fully Qualified Domain Name'
(FQDN). The distinction usually doesn't matter much, but in a context like
QuickDNS or BIND zone files, names without a trailing dot are considered to be
'relative' to some 'default domain' (the 'origin string' above). In such a
context, the default domain is appended to the end of 'relative' names. As
Chris said, what the default domain is depends on the particular server and/or
zone. This provides a very nice shortcut when working with QDNS or BIND zone
files, but omitting trailing dots, either through errors or just not knowing
about it, can cause undesired results.

Christopher Bort

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