Well I had only 2 replies to this problem, but it was very specific I admit.
The problem was also very intermittent and so I am still not convinced it's
been solved. However thanks go to:
Nickolai Zeldovich (firstname.lastname@example.org)
Bismark Espinoza (bismark@alta.Jpl.Nasa.Gov)
Both of whom pointed me in the right direction. The problem seemed to be that
we had an A record pointing to a sub-domain for which we are not
authoritative. However, the record was incorrect since the authoritative
server didn't have this, but had an SOA record for the sub-ddomain instead. (A
conflict of styles within this place I think!) Anyway, we now only have 2 NS
records (glue records?) and an MX record for the sub-domain, and it all looks
> I'm not sure that this is strictly a Sun question or just more DNS related,
> but since I have no Network News access (to any DNS specific newsgroups) I
> thought I'd try the list.
> We run a caching-only DNS on our mailhub - a sun Ultra 1 using Sun's own
> named. We have found though that occasionally it seems to lose the A record
> for one of the local sub-domains. It retains the NS and MX records, but not
> the A record stating where the actual machine is. This causes the mail to
> bounced. E.g. the non-authoritative records look like:
> pbs.plym.ac.uk preference=8, mail exchanger=pbs.plym.ac.uk
> pbs.plym.ac.uk nameserver= pbs.plym.ac.uk
> pbs.plym.ac.uk nameserver = cassandra.pbs.plym.ac.uk
> Authoritative records:
> pbs.plym.ac.uk nameserver = pbs.plym.ac.uk
> pbs.plym.ac.uk nameserver = cassandra.plym.ac.uk
> cassandra.pbs.plym.ac.uk internet address = 126.96.36.199
> This doesn't work, since the MX record says mail goes to pbs, but where's
> pbs? It obviously doesn't go to the first NS since it still doesn't know
> where that (pbs) is, and doesn't go to cassandra despite having the A
> When the caching-DNS *does* work the following line:
> pbs.plym.ac.uk internet address = 188.8.131.52
> appears in the non-authoritative section, and obviously then the MX points
> something with a known A record.
> I would have thought that the caching-DNS would either maintain the whole
> the non-authoritative section (since it starts out okay, but then just
> the A record), or none of it, or go off to the primary DNS to find out
> anything it didn't know.
> I don't know that much about the DNS and its operation, and I don't
> it for our site. But I spoke to our hostmaster and he couldn't understand
> it should be doing it.
> Any help much appreciated. I have checked with sunsolve for any DNS
> but there is little that is relevant to this. I will summarise (:-) )
> We're using solaris 2.5.1.
John Horne E-mail: J.Horne@plymouth.ac.uk
Computing Service Phone : +44 (0) 1752 - 233911
University of Plymouth, UK Fax : +44 (0) 1752 - 233919
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