Forwarders.......

Jim Reid jim at rfc1035.com
Mon Jun 19 17:52:16 UTC 2000


>>>>> "erik" == erik c pelletier <erik.pelletier at circle.com> writes:

    erik>     If the internal name server doesn't have the records for
    erik> the requested host in it's zone data or cache I would like
    erik> it to forward the
    erik> query to my external name server. For example, both the
    erik> internal and external name servers are both authoritative
    erik> for xxx.com. If someone looks up machine1.xxx.com and it's
    erik> not in the db files of the internal name server I want it to
    erik> forward it to the external server.

You can't do this. If a name server is authoritative for a zone, by
definition it knows ALL the names that exist in that zone. So if
machine1.xxx.com isn't in the internal version of xxx.com, the name
servers for that domain will return NXDOMAIN when that name is looked
up. After all, those servers know *for sure* that the name doesn't
exist. [If it did, it would be in the zone file for xxx.com. QED.]
There's no conditional forwarding mechanism in BIND: "if name server
foo says bar doesn't exist, repeat the query to foobar". I don't think
any other name server provides such a feature either.

What you could do is delegate a domain on the internal DNS for the
external hosts and addresses - say ext.xxx.com - so that internal
users can lookup the external hosts.

    erik> I've used the forwarders directive and forward-only and
    erik> neither seem to have an effect. It appears that since name
    erik> i'm looking for is within the
    erik> authoratative zone that it simply says it's not available.

Correct.



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