Re: Tips for DNS zone administration

[Robert Elz <kre@munnari.OZ.AU>]

    Date:        Sun, 22 Apr 2001 11:01:05 +0200 (CEST)
    From:        Mats Dufberg <dufberg@nic-se.se>
    Message-ID:  <Pine.BSF.4.30.0104221054260.4948-100000@spider.nic-se.se>

  | Do you mean that is bad to have
  | 
  | namn.se. soa ()
  |          ns  jox.namn.se.
  |          mx  jox.namn.se.
  | jox      a   192.0.2.10

I probably wouldn't use the word "bad" for any of these, perhaps
"less than ideal".   Of all the cases, sharing an MX name and a NS
name is probably the least of a problem, as neither is known by
anything but the DNS, so both can easily be discarded if needed.

That is, if you wanted to change the IP address of your nameserver,
but couldn't make the 192.0.2.10 address vanish from who knows where,
you could just change "jox" to "sox" in the NS and MX records, create
a new A record, fix the delegation at the parent, and you're done.

  | or do you mean
  | 
  | namn.se. soa ()
  |          ns  namn.se.
  |          mx  namn.se.
  |          a   192.0.2.10

That one, along with

	namn.se. soa (...)
		 ns  www.nanm.se.
	www	 a   192.0.2.10

are about the two worst examples, as there there's no possibility at all
to change the name if the old address simply won't go away (people keep
getting 192.0.2.10 as the A record long after you've changed it, and you
can't work out why).  That is, apart from abandoning namn.se - and that's
certainly a sub-optimal solution.

NS records are the one that causes the most of these problems, as they're
the RR type that causes (legitimate) permanent caching of the A record
(glue) in other nameservers.  If you give the NS record a throwaway name,
you can throw it away whenever convenient, and just create a new name.
Then any ancient glue A records that float around the DNS won't cause anyone
any problems (they relate only to old nameserver names that are no longer
used by anyone for anything).

kre