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Re: Virtual DNS questiona and reverse lookup table conflicts

Daniel B. Thurman wrote:

[WARNING!  This is a long discussion!]

Is it possible to have a single DNS server support
two different domain names, with each domain
name having it's own forward and reverse lookups?

The problem I seem to run into is that of reverse
lookups; I cannot seem to figure out just how to
have common reverse IP lookups separated so that
it returns the correct domain name based on the
domain name itself.


My goal here is to support redundancy by having two
separate servers, each supporting two domain names
so that if one server drops dead, the other server will
take over and also, I really do not want to have 4 different
servers, two for each domain name so, it is about cost
as well.

Does this scenario make any sense at all?

I have looked for examples on the Internet but I could
not find anything that can shed some light on this. Perhaps
someone can point me in the right direction or - perhaps this
is a nutty idea and there is a better way?

Kind regards,

The difficulty with what you want to do may be that you shouldn't want to do it.

DNS is actually two sets of services namely address resolution for domain names and name resolution for Internet addresses.

In the first instance any number of domain names can resolve to a single address i.e., mail.x.net and www.y.net can both resolve to the same IP address. This information is set up for each domain irrespective of what the IP address is. Indeed, and domain name can resolve to several IP addresses for load balancing or redundancy.

In the second instance an IP address can only resolve to a single Internet domain name and the reverse lookup resolution often is done on a computer that is different than the computer providing the forward resolution because it must be done by the entity that owns the network e.g., your ISP.

When a remote host looks up the name of a computer through reverse DNS lookup it only provides the address to the server registered as the owner of the address space and each address can have only one (canonical) name at any given instant. If it were otherwise the name server would never know which name to return in response to the reverse lookup query.


John Cornelius

"I may not be totally perfect, but parts of me are excellent."
Ashleigh Brilliant, 1979

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