Re: Should a nameserver know about itself?

[bert hubert <ahu@ds9a.nl>]

On Wed, May 09, 2001 at 04:33:11PM +1000, Bruce Campbell wrote:

> We've assumed (in writing one of our automated delegation tests) that a
> given nameserver is 'responding' if it knows about itself, ie, can supply,
> when queried, an A/AAAA/A6 record and/or a PTR record for its own name/IP
> address.

This is not necessarily the case and it is also not needed in the general
case. The PTR is never needed when resolving names, in any case.

If a query has reached your nameserver, someone obviously found out its
name and address. You would only need to supply details if they can't be had
anywhere else.

This would go if you were authoritative for EXAMPLE.COM, and you receive a
question for WWW.FRANCE.EXAMPLE.COM, and you list NS records for
FRANCE.EXAMPLE.COM, but their nameservers are themselves in the
FRANCE.EXAMPLE.COM domain.

However, as you delegate IN-ADDR.ARPA, this would only occur if you'd enter
your nameservers in an IN-ADDR.ARPA zone as well which you normally wouldn't
do. But you probably know this.

> Unfortunately, we're running into a number of delegations that are failing
> as the given nameservers fail both of the above tests, ie, the given
> nameserver cannot supply any information about itself.
> 
> Is the assumption that a nameserver should have information about itself
> correct?

It is not. It is however very often the case that a nameserver is able to
supply an IP address when asked for an A of its name. Many authoritative
nameservers will happily recurse for you. Also, even servers which are not
willint to recurse for you will happily dish out data from the cache it
maintains for clients is *does* recurse for.

An example:

$ dig ns3.exodus.net @ns3.exodus.net
;; ANSWER SECTION:
ns3.exodus.net.		1d11h19m15s IN A  206.79.240.13
(some time later:)
;; ANSWER SECTION:
ns3.exodus.net.		1d11h17m10s IN A  206.79.240.13

ns3.exodus.net is not authoritative for exodus.net, and for example, does
not know the name for www.exodus.net. So if it knows its own name and IP
address, this is mostly due to good luck. If your nameserver is unable to
supply an A for its own name, you may wonder if other people ARE able to
supply one.

Perhaps you can supply the output of the fine tool 'dig' in the cases where
your delegations are failing. 

Good luck!

Regards,

bert hubert

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