naming dns servers

[Kevin Darcy]

Barry Margolin wrote:

> In article <9m44oq$2ge at pub3.rc.vix.com>, iTypical Male  <mr_t at dr.com> wrote:
> >I've been learning about DNS, setting up, etc, etc lately, but I still
> >have one question. Many times when you whois a domain (let's say
> >domain.com), you'll see it's name servers listed as something like
> >ns1.domain.com. I'm confused since clients look up your DNS server to
> >get your IP address, how could your DNS server have a subdomain itself?
> >I know it can, obviously, since many servers are set up that way.  How
> >do you setup your name server to use a subdomain of your domain?
>
> This is a very astute question.  The solution is something called "glue
> records".  If the name of the server that's hosting a domain is within the
> domain itself, the parent domain has to have a copy of the address record
> for the hostname.
>
> So in the COM domain, the following records will exist:
>
> domain.com.     IN NS  ns1.domain.com.
> ns1.domain.com. IN A   1.2.3.4
>
> That A record is a glue record.
>
> When a query comes to the COM nameserver for something in the domain.com
> domain, it will return *both* of these records in the referral.  This
> avoids the chicken-and-egg problem.

Note that the downside of glue records is that if you ever want to change them,
you have to make sure to change them in *both* places (i.e. in the zone itself and
in the parent servers, usually via your registrar). Failure to do so will result
in stale values being seen by at least some nameservers.


- Kevin