That is exactly the situation of original question - having two ips for same dns server. It is not possible to register new dns server this way but long time ago when internic dns/whois system was originally introduced (pre 1990 to around 1994) it was possible and some companies did that, plus I think some of it came out of original hosts files maintained by NSF network participants and how it was converted that domains had one dns server with multiple ips (this is before my time; this is what I'v been told by older sysadmin who originally introduced me to dns in around 1991) but I indeed seen multiple ips for first one or two dns servers for some of the oldest domains (xerox had it, ibm I think; great number of edu domains - these all disappeared when transfered to educause), lately these old dns records all have been disappearing. Now it appears there is reverse situation - some registrars allow (and verisign no longer gives an error) to register dns servers in different domains all pointing to the same ip. I belive they may have some stupid idea to help/encourage using shared hosting and preserve ip space.
On Thu, 4 Apr 2002, Allan Liska wrote:
Yea, apparently in January Verisign changed their long standing policy of allowing only one name server to be registered per IP Address. To confuse matters even more, I don't think all of the registrars support this, and I have not seen anything official from ICANN (not that anyone cares what ICANN thinks).
I'm not certain that this is entirely accurate. Certainly, ns0.ja.net has had two IP addresses for as long as I can remember (at least for the last five years...) and has been happily reflected in the whois and .net zone.
-- Paul