Multiple DNS Servers

Kevin Darcy kcd at daimlerchrysler.com
Thu Apr 20 22:39:01 UTC 2000


There is really no such thing as "conditional" forwarding in BIND 8. There
is, however, "selective" forwarding. The difference is more than semantic:
selective forwarding works *unconditionally*, i.e. has no relation to
events or state, but is specified on a zone-by-zone basis, i.e. all queries
in a specific zone X should be forwarded to a specific set of servers Y, Z,
etc.. In your case, you'd set up a zone of type "forward" for your business
partner's domain,  let's call it "partner.com". And also in the zone
definition you'd specify "forward only" and a "forwarders" clause
containing the addresses of the partner's nameservers. So it would look
something like:

zone "partner.com" {
    type forward;
    forward only;
    forwarders { x.x.x.x; y.y.y.y; };
}

In your situation, selective forwarding would probably be better than
conditional forwarding anyway, which would waste time and resources sending
queries to the wrong places.

A couple of other alternatives to consider, depending on your performance
characteristics and/or requirements, or redundancy requirements, would
include stub or slave zones.


- Kevin

Dave_Walsh wrote:

> We are a satellite organization of our parent organization.  At present,
>
> all of our Win95 PCs point to my local DNS server with a forward
> statement
> to our parent organization's DNS server for name resolution.  In other
> words, anything not resolved locally, will be forwarded to our corporate
>
> head office (where our Internet access is also).  We've recently
> acquired a
> project with a business partner that requires only our location to have
> access to the partner's DNS server so I can resolve names in their name
> space.
>
> What's the best approach to accomodate all my needs?  I must be able to
> resolve local IP names, corporate names in the corporate WAN, Internet
> names (via corporate) & the names at our new business partner.  Can I
> put on a second
> forwarder statement on my local DNS server that will effectively say,
> "if
> you can't resolve it yourself, try the corporate DNS, if you can't
> resolve
> it there, try the partner DNS?".
>
> Mr. DNS says that conditional forwarding of BIND 8.2 will do it.  I'm
> pretty new to DNS.  Can someone please advise.
>
> TIA
>
> Dave
>
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