Not so clear

[Kevin Darcy]

lg042-5 wrote:

> I can't see the difference between :
> forwarder slave, forwarder, caching only server...

A slave is a nameserver that replicates a zone in its entirety from some
other nameserver.

A forwardING nameserver is one which sends queries to some other
nameserver (or a set of nameservers) called forwardERS, for any name it
doesn't know about.

A caching-only nameserver is one which does neither of these. It just
knows implicitly about some servers where it can get information about
the root zone. Given that root-zone information, it can then resolve any
name by working its way down the namespace hierarchy.

Note that in later versions of BIND, you can mix these almost any way
you want, either as a default or on a zone-by-zone basis. You could
slave some zones, forward other zones, and just be a caching server for
everything else. Or you could forward by default, but slave certain
zones. Or forward by default and "cancel" forwarding for certain parts
of the namespace, in which case the nameserver would be acting as a
"caching-only" server for those branches of the namespace tree. There
are many different combinations.

There's also another kind of zone type called "stub". This is kind of a
compromise between slaving and forwarding -- the nameserver replicates,
but only the "stub" information (basically just a list of nameservers
which serve the zone). It doesn't offer as much redundancy as being a
slave, but the transfer overhead is smaller, and it generally
outperforms and is more robust than forwarding (assuming one has full
network connectivity). In cases where you have network connectivity
issues, sometimes forwarding or slaving are the only choices.


- Kevin